It would have been much more helpful to go into the question knowing that there is specific category called "Principle Conform." That category might be considered a derivative of MSS, but the question is made much easier knowing that we are to find the principle in the answer choices that reflects the information in the stimulus. A typical Principle Conform stimulus might ask "The reasoning above conforms most closely to which one of the following propositions?" Of course, in this question we have to replace "situation" with "principle" and "generalization" with "proposition." I must admit that it's a sticky wicket.

@LiviaLSAT Yes I agree. The word "only" should indicate a necessary condition. One is a lawyer only if one has passed the bar exam. A biconditional means necessary and sufficient: One is a lawyer if and only if one has passed the bar exam. If you are a lawyer, you have passed the bar exam, and if you have passed the bar exam then you are a lawyer. But a biconditional doesn't work for that because passing the bar exam doesn't automatically mean you practice law.

Wow this was a tough question for me and I got it wrong. After much analysis I think I got to the crux of the argument and that leads directly to the conclusion. It boils down to the following. The premises are made of condensed information:

P1: Animals have pheromones and their sexual behaviors are involuntary.

P2: Humans have pheromones and their sexual behaviors are voluntary.

C: Pheromones play no role in human sexual behavior.

Obviously the big gap is the assumption that "voluntary" = "pheromones play no role human in sexual behavior," and that is a big assumption. And I got the question wrong because I was thinking pheromones = chemicals; chemicals = control. But the stimulus says involuntary = chemical control... and does not indicate what types and percentages of chemicals (or what ratio of pheromones) combine to result in the right mix of chemicals to produce involuntary action. Therefore, chemicals could be involved in human sexual behavior still, just not to the level of control. The step necessary to bridge to the excessive claim that pheromones play no role whatsoever is "if sexual behavior in humans is voluntary, then pheromones play no role." That is exactly what we find in answer choice B.

My "post-mortem" reasoning devoid of astronomical knowledge was as follows: Assuming there is no other way to measure distance, an observer from Earth sees stars of varying brightness levels. Obviously one could assume the ones that appear dimmer are further away if all things are equal (if all stars had the same intrinsic brightness). But things are not equal. Some stars are inherently brighter than others. So with that let's imagine we see a star that is 25% as bright as the average star. With no way to measure distance, we could assume it was either old and close or young and far. But the key piece of information we need to make that conclusion (younger = brighter) is not in the stimulus. Once we have that we can see that the "earlier estimates" were wrong because they erred too much on the "old and close" side of the formula, so much so that it would make them impossibly old. So correct that to younger/brighter/further and we can make sense. This is actually the second time I have encountered this question. I think I guessed right the first time simply because the conclusion mentions age and distance, a premise establishes a relationship between brightness and distance, so a logical link between the two is age and brightness. I missed the question on my second encounter with it, hence my post-mortem analysis.

I made up a parallel argument to help me see why I got this wrong. Here it is:

A new facility was created to reduce the number of tigers escaping from the local zoo. However, although doing so worked in other cities, it did not work here. Which answer choice does the least to help resolve the apparent discrepancy:

A) The construction crew was later found to have ties to an international tiger theft ring.

B) The zoo's director hates to see tigers locked up; he has the keys and is mentally unstable.

C) The construction crew mistakenly thought the cage was for housecats.

D) Of the tigers that escaped, 75% confessed their guilt.

The last sentence in the stimulus tripped me up. My mind didn't smoothly translate "avoid a decrease" and "not decrease" into its opposite and then link it to "will decrease" while juggling with necessary condition "only if." I think it is partly because there is the added confusion of the mental pair (decrease vs. increase) going against the pair (decrease vs. not decrease). Difficult question.

I do not see the difficulty that J.Y. indicates in the video. Small vacuum tubes are a subset of all vacuum tubes. If no vacuum tubes allow the capacity of electrical current that is necessary to make them preferred, then the necessary condition fails, game over answer A. Perhaps J.Y. misread "current" capacity as "heat capacity at present."?

This is made easier if one uses Venn diagrams. Put "almonds grown in CA" in the center circle. Then each of the concepts "grown for domestic consumption" and "requiring intense irrigation" have to overlap that circle more than 50%. There necessarily has to be some almonds in the overlapping zone.

It is argued by some that I should spend less money on my girlfriend. But let's look at the real cause of my bankruptcy: My gambling problem. Therefore it is not warranted to say that I should spend less money on my girlfriend.