imo, the hardest part of this question is figuring out the main conclusion, which is "we will not be able to determine (that there are sentient beings outside our solar system etc.) anytime in the near future". when you look at all of the answer choices, only answer choice D has a link to the idea about existence. all of the other answer choices are about communicating with them, and then A is just off the mark. so once you can recognize that, D being the right answer is clear. Hope this helps someone.

Something that is helping me navigate these questions is to think about the fact that the author's conclusion is not proven, its under question. so it shouldn't be the sufficient condition in our answer choice, because if we are unsure if a sufficient condition is triggered, then the whole thing is basically moot. In this case, the conclusion was that the company bears responsibility for what happened. In answer choice E, we see this conclusion as the necessary condition, with the sufficient condition being 'if those consequences were preventable'. We know that the consequences were preventable, the company could have investigated the safety of T before exposing its workers to it. So, the sufficient condition is triggered, and therefore the necessary condition follows, thus proving (or most justifying) our conclusion. Answer choice B does the opposite of what we are looking for. It places our conclusion as the sufficient condition, which basically leaves us in the same place we started. The conclusion is the author's opinion after all, so how can we ever know if this condition will be met?

Pat. I would like to speak with you.

@16dnholli

I also got a bit tripped up by this at first, but when doing group 4, you should never include 'cannot' in your negation. You only look at what 'cannot' is modifying and negate that.

So in this case, I am singling out being happy as one of the conditions. That would give me these two correct translations.

Serious financial problems --> /happy

Happy --> /Serious financial problems

Hope this helps.

@MGonz6

It all has to do with the meaning of the indicators themselves, and what they imply. The difference is highly important because for example, if you were to say "I will not shower unless I eat something first", and you correctly negated the sufficient, you would get the answer:

Shower --> Eat something first

/Eat something first --> /Shower

If I tried to negate the necessary instead, I would end up with the following:

/Shower --> /Eat something first

Eat something first --> Shower

As you can see, mistakenly applying the wrong rules gets you results that confuse the sufficient for the necessary. It entirely hinges on the word 'unless'.

In my example, "I will not shower unless I eat something first", I can rephrase it in my mind to say:

If I do not eat something first, then I will not take a shower. OR I will take a shower only if I eat something first.

As you can see, this is the same as our correct translations from above, where we negated the sufficient.

It would not make sense to try to rephrase it to say something like,

If I eat something first, I will take a shower.

For all we know, I could eat something and still chose to not take a shower. But we know for a fact that if I do shower, then I did eat something first.

In one of our examples from this lesson, "Lazy cats never develop heart disease",

I can rephrase it in my mind to mean "If I am a lazy cat then I will not develop heart disease", "All lazy cats do not develop heart disease", etc.

As you can see, I am negating the necessary when I am rephrasing this in my mind, and this is entirely because of what the word 'never' is implying in the sentence.

I hope this helps!

Hoping to get a little clarity on when using 'or' vs. 'either/or' affects the overall meaning? In the first example, "You must sit at either one end of the table or the other", it was said that the removal of 'either' did not affect the meaning, given that you must sit at one end and its not possible to sit at both. But in which instances does the use of 'either/or' vs. just 'or' impact the meaning? Could it ever just be 'either' with no 'or'? Thanks!