I'm assuming that you are confused with how there is an "and" in the sufficient given the stimulus provided. The way to conceptualize this is that the information provided between the commas is seen as another qualifier. Because it says "Anyone infected by the virus will, after a week, produce antibodies to fight the virus." we know that not only is having the virus sufficient for producing antibodies, but the being infected for over a week is also sufficient.

Let's say that I add another premise. "I have been infected with the virus for 3 days.". Take Lawgic out of it and look from a purely English standpoint. You wouldn't be able to infer a valid conclusion because the sentence explicitly says that after a week I will produce the antibody. Because of this relationship, you know that after a week must be another sufficient indicator. Being infected is not the only thing sufficient for producing antibodies.

Yes, it means the same thing. You are just taking the contrapositive of one. If they are flowers in the garden, then they don't bloom in the winter (fig --> /biw). The contrapositive would be if they bloom in the winter then they cant be flowers in the garden (biw --> /fig).

I understand your train of thought, but I think you are looking at argumentation through our own worldly experience. What I mean is this:

If you and I are having a conversation about when I will get to work tomorrow and I say "I always get to work on time when there is no rain. There is 0% chance that there is rain tomorrow. Therefore, I will get to work on time." You would most likely attack my premises by either pointing out that I don't always get to work on time or that there isn't a 0% chance of rain. This is how we tend to attack arguments in the real world and we are able to because we have additional information that supports or attacks my premises.

On the LSAT, we do not have that additional information. We don't know if the author is always on time when it doesn't rain. We have limited information so we must take the premises to be true. Essentially, all premises are the same level of truthfulness. Yet, how they connect with each other to prove the conclusion(support) varies widely. Thus, not all arguments are equally strong but all premises can be taken as true.

I hope this helps.

Answer choice c was already accounted for in the stimulus because the conclusion says "But this catastrophe was probably not responsible for most of these extinctions". By saying "most" we can make a reasonable assumption that at least some of the extinctions of dinosaurs came from the asteroid impact. Answer choice c restates this because by saying "Fossils have been discovered of a number of dinosaurs that clearly died as a result of the asteroid impact that produced the Chicxulub crater." If the answer choice said "many of the dinosaurs fossils" then it would be a direct contradiction of the stimulus. But, without a quantity then we can assume that this is a restatement of the conclusion.

This question was difficult, but I think that mindset going into the answer choices can make it easier. For RRE questions that are EXCEPT, 4 answers that reconcile and 1 that doesn't, I like to approach it by understanding that there will be different "types" of answers. What I mean is that the first thing that comes to mind for this question is looking for answer choices that show that foods are "superior" to supplements and the timing difference. These are easily spottable because they are the blatant differences between the two groups. However, the part that I'm always aware of for RRE questions like this is the answer choices which show that there might not really be a discrepancy. In this case it was that there was an alternative reason/hypothesis for why the people who have high intake of BC had lower chances of cancer/heart disease. Conversely, you could look for an answer choice that affirmed that there was an alternate reason for why the 12-year group had no difference. What if the 24-year group was comprised of 1,500 non-smokers and the 12-year group was comprised of 20,000 smokers? Well, then that could also explain the "discrepancy" between the two study groups.

It was appropriate to use 140k instead of 150k because the assumption with this experiment is that both of the control groups are equally split up. Meaning if there are 10k people in control group A (smoking group) living on street X then there will also be 10k people in control group B (non-smoking group) living on street X. Thus, if you have the equal distribution between control groups then you have eliminated all other potential causes of lung cancer. Since 10k people got cancer that did not smoke, then we know that there was an alternate cause for 10k people in the smoking control group as well. (Remember that all other things are equal so you can make this assumption). Therefore, out of the 150k people who got lung cancer in group A, 140k (150k- 10k from other reasons) can be attributed to smoking.

Note that this is all hypothetical because it is more complicated in real life

These lessons are much more interactive and make the subject easier to pick up on then the first version was. Thank you!