Long-winded description here, but hopefully it will help you:

• FS = Fuzzy seeds

• LS = Long stems

• WF = White flowers

• TS = Thorny seapods

• CL = Curled leaves

• X = Plant X

What we know from the premises:

1. FS —> LS and /WF } Contrapositive = WF or /LS —> /FS

2. CL —> WF

3. TS —> CL

4. X —> LS and CL

Looking at what we have, #4 Can be branched into two:

a) X —> LS } Based on this, can we conclude anything from the premises? Not really - we don't have anything that LS on its own leads to. Sure, we have FS leading to LS (but not only FS, also /WF), and we have no evidence to believe that X is either FS or also leads to /WF.

b) X —> CL } from #2, we know that CL --> WF (so we can say X --> CL --> WF).

We also know, from the contrapositive in #1, that if you have WF, you can have /FS. Mind you, you can have WF or /LS, you don't need to have both.

Combining these two ideas, you have the following:

>>> X —> CL —> WF —> /FS

!!! Important to note: having LS does not break this chain! As I mentioned in (a), having LS doesn't prevent you from having anything (you can say that the contrapositive from #4, if you don't have LS you don't have plant X, but that's irrelevant to our example here). Also, for the contrapositive of #1: you know you have WF, and it's either WF or /LS that leads you to /FS. You satisfy that condition - you know you have WF, guaranteeing /FS (whether you have LS or not - in this case, you do!)

Now, let's see:

• Plant X: has Curled leaves.

• Plant X: having curled leaves --> has White flowers.

• Plant X: having CL and WF --> does not have Fuzzy seeds.

Looking at answer choice C, that's exactly what is states: Plant X has White flowers but not fuzzy seeds, which is exactly in line with X —> CL —> WF —> /FS.

The way I understood it:

• P1. FQ and /W

• P2. MP

_____

• Conclusion: Hire Delacruz

What we know: Don't hire Krall, because Delacruz is a candidate and fully qualified.

So, Delacruz = FQ. OK.

AC [E]: "None of the candidates already works for Arvue, and Delacruz is the candidate who would be most productive in the new position."

a) What we know from this: all candidates are /W (both Krall and Delacruz as well).

• For P1: Delacruz = /W, Krall = /W; so for P1, we know Delacruz is both FQ (from stimulus) and /W (from the AC)

b) Delacruz = MP (so for P2: we know that Delacruz fits this as well; it does not tell us anything about Krall, but if Delacruz is MP, it's safe to assume Krall is not)

So, what do we have here for each:

Krall = /W.

Delacruz = FQ and /W, and also MP.

Well, looking at

• P1. FQ and /W

• P2. MP

_____

• Conclusion: Hire Delacruz

Seems like this fits with the trigger for the rule.

Conclusion: The general principle—if one ought to do something then one can do it—does not always hold true.

• Should --> Can = Not always true

--> In other words: the idea that "because you should do something, you can do it", is NOT always true.

Evidence: You make a promise, you run into a traffic jam, you can't keep it.

• Promise --> (unforeseen jam) --> /Can

Let's write it out.

1. Just because you should do something, it does not mean you can do it. } OK.

2. You make a promise to someone. } The (albeit unstated) idea is that you SHOULD keep your promise (from the general idea that promises should be kept).

3. Combine #1 and #2 --> Just because you should keep your promise, it does not mean you can keep it.

4. Something happens to you (like a traffic jam), and you cannot keep it. } We know from above that you made a promise, and that you can't keep it.

   But... just because you can't keep a promise (for whatever reason), does it mean that you SHOULD not keep it? In other words, the fact that you can't keep your promise relieve you from the obligation to keep your promise?

   Clearly not; you SHOULD still keep (or try to) your promise, even if you can't actually do it.

5. It's important to differentiate between what you should/shouldn't do versus what you can/can't do. You can have situations when you should and can, or should and can't [the latter being our conclusion, essentially, as it states the former is not always true]

1. The diet of Heliothis subflexa caterpillars consists entirely of fruit from plants of the genus Physalis.

2. These fruit do not contain linolenic acid, which is necessary to the growth and maturation of many insects other than H. subflexa.

3. Linolenic acid in an insect's diet is also necessary for the production of a chemical called volicitin.

• V -> L

1. While most caterpillar species have volicitin in their saliva, H. subflexa does not.

• HS -> /V

• C -m-> V

_____

You have: most Cs are Vs, and all Vs are Ls. Therefore: if most caterpillars have volicitin, and all who have volicitin guarantee linolenic acid (i.e. volicitin leads to linolenic acid, in other words = is a source of acid), then most caterpillars have sources of linolenic acid in their diets.

Is the idea/trick for C also that, it states "... patients who change their relationships with other people will thereby find relief from at least some of their troubles." --> we can't conclude whether it's positive change (like it says in the stimulus)? What if it's referring to negative change (i.e. deterioration of relationships)? Does this mean that the deterioration of relationships (i.e. change in relationships) will allow people to find relief from some of their troubles?

A = Freelance journalists

B = Sell their work to magazines that have lax editorial standards

C = Self-respecting writer

This gives us the following:

• Some A are B.

• No C is B.

  _____

  Some C are not A.

Look at [C], which is identical in terms of structure:

A = Students

B = Prefer history to mathematics

C = Member of the Calculus Club

• Some A are B.

• No C is B.

  _____

  Some C are not A.

AC [E]: The conditions at a pond are beneficial to turtles only if the water in the pond is not acidic.

P1. Thriving —> Beneficial

P2. Acidic

_____

/Thriving population of turtles

[E] Assumption: Beneficial —> /Acidic } Contrapositive = Acidic --> /Beneficial

Contrapositive of P1: /Beneficial --> Thriving

So we know you have Acidic (from P2), which leads you to /Beneficial (from contrapositive of the assumption), which then leads you to /Thriving (contrapositive of P1), which is your conclusion.

P1. Thriving —> Beneficial [or, /Beneficial --> /Thriving]

P2. Acidic (this is a premise on it's own, we can't use the contrapositive, so we have to take it as is and see if any of the other premises allow us to draw the conclusion with this one being as is)

Assumption: Beneficial —> /Acidic [or, Acidic --> /Beneficial]

_____

/Thriving population of turtles

I would just like to clarify AC (C). Looking at the premises:

1. Valuable —> Well-run

2. Large and well-run -s-> FT

3. Small and well-run -s-> PT

4. Large and Valuable [and well Run] -s-> Open all year

5. Small -m-> /Open all year

"Some zoos that make valuable contributions to their communities have only part-time veterinarians on staff."

We know that if a zoo makes valuable contributions, it is well-run (P1). So if we know that the zoo makes valuable contributions, why is it wrong to assume that it is well-run? How is this reversing P1 (i.e. Well-run -> Valuable)? Because then, if it makes valuable contributions (which, being a sufficient condition, guarantees that it is well-run), you can say that it's a small zoo that is well-run and only has PT (i.e. PT) on staff. Why do you strictly have to go off of P3?

P1: Valuable --> Well-run

P3: Small and well-run -s-> PT

AC [C]: Make valuable contributions only have PT } If you make valuable contributions, you are well-run (from P1). And then you can use P3 [Small + well-run -s-> PT].

When explaining P4 for AC (D) at 9:51, the instructor says "valuable contributions implies that they are well-run", and you can replace Valuable with Well-run in P4 (seemingly from what we have in P1). So for P4 - (Large and Valuable --> Large and Well-run). So in AC (C), I have "zoos that make valuable contributions" - here, it can't mean "zoos that are well-run"?

"For several centuries there have been hairless dogs in western Mexico and in coastal Peru. It is very unlikely that a trait as rare as hairlessness emerged on two separate occasions. Since the dogs have never existed in the wild, and the vast mountainous jungle separating these two regions would have made overland travel between them extremely difficult centuries ago, the dogs must have been transported from one of these regions to the other by boat, probably during trading expeditions."

Conclusion: The dogs must have been transported from one of these regions to the other by boat, probably during trading expeditions.

• Support: The dogs have never existed in the wild, and the vast mountainous jungle separating these two regions would have made overland travel between them extremely difficult centuries ago.

Looking at the two popular ACs (negated):

A - Hairless dogs have at least once have been found anywhere except in the regions of western Mexico and coastal Peru —> ultimately, the conclusion talks about the dogs being transported between western Mexico and coastal Peru by boat. The fact that they may have been found elsewhere, does it impact the conclusion about the transport between those two countries? Not really.

E - Centuries ago it was NOT easier to travel between western Mexico and coastal Peru by boat as by an overland route. —> The implication is, that it was the travel was either as equally as hard or equally as easy (not one was easier/harder than the other). What does this mean?

• It wasn’t more difficult using overland route than by boat (like the premises state), it was either equally as hard or equally as easy. If this is the case, then why would you then conclude the dogs being brought to one of the countries from the other HAD to be by boat? Yes, the premises state that since “vast mountainous jungle separating these two regions would have made overland travel between them extremely difficult centuries ago” it had to be by boat, but if we assume that travelling by overland route was not any harder/easier than by boat, than you can’t really say with 100% certainty that it MUST HAVE BEEN by boat (and much less that it was during trading expedition)

 The higher the average fat intake among the residents of a country, the higher the incidence of cancer in that country; the lower the average fat intake, the lower the incidence of cancer. So individuals who want to reduce their risk of cancer should reduce their fat intake.

Premises: Average fat intake impacts incidence of cancer (higher AF leads to higher cancer incidence; lower AF leads to lower cancer incidence)

Conclusion: if you want to reduce risk of cancer you should reduce your fat intake.

!!! >>> Gap: average fat intake impacts RISK of cancer -> look for an AC that sort-of is related this idea somewhat (it's related to the conclusion).

The premises talked about incidence of cancer, whereas the conclusion talks about the RISK of cancer - two different ideas. Connecting the two gives you the notion that average fat intake impacts the RISK.

Looking at ACs A and B seem irrelevant. No mention of risk (or even hint).

Look at C and E:

• C: even if Cancer is a prominent cause of death in a country with a low average fat intake, it's also the case for a country with a high average fat intake. It doesn't explain the difference why in one instance it may be higher or lower.

• E: if someone is an outlier or a minority with respect to their low fat intake, that doesn't explain the difference.

Now, look at why AC "D" could work: country has high average fat intake, and higher incidence of cancer; but also high pollution. If you reduce the fat intake in this country [which is what supposedly we need to lower RISK of cancer], are you necessarily because of this lowering your risk of cancer? No, because your risk of cancer can still be high because of the pollution, even with lower average fat intake. So lowering your average fat intake, in this case, will not necessarily lower your risk of cancer.

For AC (A):

1 . X - good luck charm

2 . ABC used X. - AFS use charms

3 . ABC is Y. - AFS win lottery

_____

Conc: X leads to Y. - good luck charm leads to winning lottery

/F —> /SI } There is no individual freedom without social integrity

/GL —> /SI } Pursuing the good life is not possible without social integrity

________

/F —> /RL } There can be no individual freedom without the rule of law

Assumption: /F --> /SI —> /RL (we know that /F leads to /SI; how can we thus get from /SI to guarantee /RL? = hence, the assumption). The /GL (good life) component doesn't play a role in the argument/assumption.

I'm wondering, if you break down the parts:

1. "Any conceivable form of life depends on the presence of adequate amounts of chemical elements heavier than hydrogen and helium".

2. "Our sun has an unusually high abundance of these heavier elements for its age."

If we say that Statement #1 doesn't support Statement #2 (which makes (B) wrong and (A) right), then if we take #2 on its own, how would we know what "these heavier elements" that it's referring to? Sure, we don't know what those heavier elements are specifically, but we can infer they're heavier than something (by comparison). In the question, we know "these heavier elements" are those that are heavier than hydrogen and helium, without knowing what they are exactly. How, then, is #1 not supportive of #2?

If the question was "Conditions in our solar system have probably favored the emergence of life more than conditions in most other solar systems of similar age. Any conceivable form of life depends on the presence of adequate birds and insects in the solar system, and our sun has an unusually high abundance of these heavier elements for its age." then you can reasonably infer that Statements 1 and 2 are without evidence and independent of each other. But if there's an inferred comparison to something (even if it's not named), how does that not support the second statement?

Hi folks, this is kind of how I was able to determine the answer was (C) - this may help you:

• Conclusion: Most who filed did so as a "money-grab" so-to-speak --> They filed not because of a legitimate injury/didn't have a legitimate reason to/for filing late.

• What weakens this argument: there was a legitimate reason why the employees filed later, and not due to a "money-grab" (my word)

A) Workers cannot file for compensation for many job-related injuries, such as hearing loss from factory noise, until they have left the job. —> An employee has to wait until they leave the job to file a claim = Explains why they filed later (i.e. when they were fired) (not for a money grab). Weakens.

B) In the years before the factory closed, the factory's managers dismissed several employees who had filed injury claims. —> Before, the employees would risk getting fired by submitting a claim - they waited to be fired first (in other words - the factory closing) before submitting the claims, they didn't do it when they did to gain benefits they didn't deserve (not a money grab). Weakens.

C) Most workers who receive an injury on the job file for compensation on the day they suffer the injury. —> So if you normally file day after injury, why file after plant has closed (presumably more than a day after you were injured)? This could strengthen argument, that they applied later than they normally do, because they were out for money - POTENTIAL ANSWER (when analyzing each AC one by one)

D) Workers who incur partial disabilities due to injuries on the job often do not file for compensation because they would have to stop working to receive compensation but cannot afford to live on that compensation alone. —> Explains why workers filed the claims later (couldn't afford to stop working in order to receive the compensation) (not money grab). Weakens.

E) Workers who are aware that they will soon be laid off from a job often become depressed, making them more prone to job-related injuries. —> How does this weaken? Multiple injuries (due to expectation of being fired soon) may be the reason why the claims were submitted later, not because they were out for money. Weakens.

@KarlieS @ZulymarPerez the way I understand it is, that the conclusion is "The key to quitting, however, may be as simple as replacing an unhealthy activity with a healthy one." --> if you pick a random sample of smokers (without knowing any pre-existing conditions), your results are likely to be better representative of the program's effects than if you picked people who have dispositions to have/not have success.

For example, if you said the people in the first group were more likely to be diabetic, than the fact they didn't have success may stem from this condition and not the notion that they just didn't exercise. If you apply the random sampling idea, then you're kind of inferring that we're going off of people without any special/particular conditions (which may skew the results of your studies).

@Shannell_E'llan I hope it wasn't too confusing :D I wrote it out after watching the explanation.

"After hearing testimony establishing that Alaska Natives had made many uses of sea otters before the occupation of the territory by Russia in the late 1700s, the court reconsidered what constituted a traditional item under the statute. The court now held that the FWS's regulations were based on a "strained interpretation" of the word "traditional," and that the reference to "living memory" imposed an excessively restrictive time frame."

If we say that the court re-considered, (after hearing the testimony of Alaskan Natives made uses of sea otters before the occupation of territory by Russia in the late 1700s) and subsequently held the belief that the FWS's regulations were based on a "strained definition" of the words "traditional", given the context of the passage, how is it that we can say "well the court didn't cite to what the Natives said about tradition", therefore (A) is wrong? The court, after hearing the testimony from Alaskan Natives based on how THEY interpreted tradition (as well as their practices), defined the regulations as strained, because FWS didn't (seemingly) consider how Alaska Natives have historically understood tradition.

Cheers!

Is the idea here that, for A, we're talking about "plant or animal species", which are mentioned in the conclusion, whereas B talks about "world's most endangered species"? So we know from the conclusion that regular intervention by resource managers is needed to "maintain its fill complement of plant and animal species", but the stimulus doesn't suggest that regular interventions by resource managers is needed for endangered species. Because (I suppose), technically it's possible that plant and animal species aren't necessarily among the "world's most dangerous species", which would mean that the conclusion on its own is not linked to what B is saying, because stimulus links resource managers and plant and animal species, whereas option B links resource managers and endangered species. The stimulus doesn't say anything about endangered species not surviving without interventions.

Hang with me folks, I think I figured it out (writing it out has helped me when looking at the question):

• Conclusion: we will not be able to determine if there are sentient beings on planets outside our solar system anytime in the near future UNLESS some of these beings are at least as intelligent as humans.

  ---> Why is that?: Because we will not be able to send spacecraft in near future + any sentient capable of communicating would have to be as intelligent as us.

B, C and E do not prove why we won't be able to determine if there are sentient beings on plants outside our solar system (unless said beings are as intelligent), which is what the conclusion is.

• "B": "any beings as intelligent as humans" --> stimulus doesn't say what they would want to do (i.e. communicate with sentient beings outside their own solar systems)

• "C": the fact that we won't be able to send a spacecraft to other planets isn't contingent on whether there are sentient beings living there.

• "E": the conclusion states that unless SOME of the other sentient beings is as intelligent as humans, and the premise says that ANY sentient capable of communicating is as intelligent as us. But whether these two categories overlap (as intelligent and capable of communicating) are not proving to us why we won't be able to determine whether they exist.

• "A": the fact that we won't be able to determine it in the near future doesn't mean that there are no sentient beings in planets other than Earth.

Now, looking at "D" --> "Any sentient capable of communicating would have to be as intelligent as us." --> Ooooh-kay, so if they communicate with us, they are as intelligent as us (Communicate --> As intelligent; contrapositive: /As intelligent --> /Can't communicate). So if they can't communicate, this doesn't mean that they don't exist or aren't as intelligent (just because you have /Can't communicate doesn't mean that they're absent or that, if they're there, they are /As intelligent). But the only way for us to know whether they exist, based on the stimulus, in that case, is to send a spacecraft (which we know we won't be able to do, but based on the description, that's the only way to verify whether those beings exist).

From the stimulus:

A. Has to have exemplary record: eligible (has to; without it - answer doesn't matter)

B. Exceeded expectations

C. Saved life

_____

Conclusion: Receive award

Answer choice A: Franklin and Penn risked their lives to save a child from drowning - conditions (Conditions B and C - CHECK). Franklin has exemplary record, Penn does not. (Penn is not even eligible, and should not get it, but Franklin checks all the conditions. [full disclosure]

!!! [TRICKY] Answer choice B: F and P have exemplary records and saved a child from drowning (A and C - Check). Franklin went above and beyond, Penn did not. Even though Penn did not go what's reasonably expected (failing condition B), he is still eligible for the award and could receive it despite not going above and beyond (could be for a different reason). Him not going above and beyond does not automatically disqualify him, based on the rules described.

Answer choice C: "Neither Franklin nor Penn has an exemplary record" --> Well, you can eliminate this option right there, since neither are even eligible for the award.

Answer choice D: We're not told whether they are even eligible to get the award. We can't assume they just have exemplary records at face value --> ELIMINATED.

Answer choice E: Similar as (B): they're both eligible, but the fact that Franklin has saved lives and went above and beyond does not disqualify Penn from getting it (Penn still has an examplary record and is thus eligible; he could get the award for another reason(s) that have nothing to do with going above and beyond and/or saving someone's life).

@saulgoodman13 careful, remember from Foundations in terms of the sufficient/necessity confusion:

A -> B does NOT mean /A -> /B; the contra-positive is /B -> /A.

Example:

NYC -> USA does not mean /NYC -> /USA (you can be in the USA without being in NYC; similarly, if you're not in the USA, you can't be in NYC).

@emmalemon @Raba'aAbutaleb You have to look at the Rule and Application separately in a sense. The Application in one case (Celia here) does not necessarily trigger the rule just because there are characteristics of the rule in Celia's situation. For example (in the case of D that you're asking about):

Part 1: Celia didn't read the insurance policy thoroughly. --> Ask yourself - why didn't she read it thoroughly? Is it because of the way the policy is written specifically (with a lot of jargon)? Or was she simply busy? Or was it because someone bought the insurance for her? We can't tell in this answer choice. So say she didn't read it because she didn't feel like it. Then the rule isn't triggered, because the policy wasn't read not because of how it's written, but because Celia didn't want to.

Part 2: Reasonable person in her position would assume the policy covers hail damage. --> Yes, but... again, that's the case if the person doesn't read the policy because of the way it's written. This answer choice (i.e. D) doesn't indicate whether that's the case, that she didn't read the policy because of the way it's written, and not for some other reason.

Now contrast that with B: it says specifically that, given the way it (i.e. policy) is written, a reasonable person would not have read Celia's insurance policy before signing it, and Celia reasonably expected the policy to cover hail damage.

Hang with me here folks, I think I figured it out:

Conclusion: deterioration of cognitive faculties associated with Alzheimer's disease is caused by microglia (i.e. brain’s open immune cells).

Why: Microglia (brain’s open immune cells) attacks protein BA deposits by releasing poisons that destroy healthy brain cells which impairs brains cognitive functions; deterioration of cognitive faculties (caused by microglia) can be slowed by acetylsalicylic acid.

Assumption: AA slows down the deterioration caused by Microglia. It doesn't stop or eliminate it, it just slows it down. It's like adding an extra step (I'm just drawing it out here):

Initially, we had Microglia --> Deterioration.

Now, it's Microglia --> (AA) --> Deterioration.

How does AA, when slowing what is caused by Microglia, still reinforce the idea that Microglia still leads to deterioration (conclusion)?

• Microglia = brain's open immune cells. OK.

• AA = slows down the process of brain’s open immune cells --> deterioration, but still can/leads to deterioration.

Answer choice B --> Acetylsalicylic acid reduces the production of immune cells in the brain } So REDUCING the production of brain's open immune cells makes it so that there is LESS of them, so it won't lead to the deterioration as quickly, right? Logically: more bad/good cells = more reproduction of said cells; if brain’s open immune cells lead to deterioration, and this chain/process is slowed by AA, it makes sense that AA makes it so that there are LESS brain’s open immune cells (microglia).

So we have a lot of microglia (i.e. brain’s open immune cells) which leads to deterioration of faculties; taking AA slows this process (it doesn't stop or eliminate it). How can it do that? Well, logically, it has to impact Microglia somehow, if it makes longer to get from A (microglia) to B (deterioration). Answer choice B tells us: AA reduces number of Microglia = YES, there are less brain’s open immune cells, but this lower number still leading to deterioration REINFORCES the notion that those cells that were not reduced (which are still Microglia) by AA led to the deterioration of cognitive faculties.

Conclusion: Last year’s mild winter reason for larger bird population.

Why: it was mild for bird to forage naturally and not visit feeders; they stayed home in summer range without migrating south.

Assumption: it's a strengthening question - we know that mild winter made it easier for birds to forage naturally... but what makes it so that foraging naturally (versus eating at feeders) is ALSO/ADDITIONALLY beneficial (other than the fact that the winter was mild)?

---> Answer choice C: eating at feeders = more dangerous because of predators; foraging naturally = easier because of the winter (milder makes it easier), but ALSO because it's safer (less vulnerable to predators).