tldr; experiment design framework (my take). The conclusion essentially states that something's wrong with the design of the experiment. Therefore, answers that fix the experiment will weaken the conclusion, and answers that spell out the flaw will strengthen the conclusion.

The premises state that there are two things that hard to control for: concentration of killer molecules in the bag and effective concentration (proportion of killer molecules in the soil).

(C) pretends to strengthen the experiment by saying that we don't need need to control for one of the two variables (molecule breakdown in the soil)

(D) pretends to strengthen the experiment by controlling for one of the two variables (molecule breakdown in the soil)

(E) pretends to weaken by asserting that only one of the two molecule forms was analyzed

(A) pretends to control for the difference between the molecule forms by reiterating the information from the stimulus

(B) weakens the argument by showing that the experiment controls neither for the concentration in the bag nor for the concentration in the soil.

It feels like somewhat casual explanations didn't do justice to this question. (B) seems to be baiting for sufficiency-necessity confusion which could work on those who's assumed that hiccups is necessary for Ebola.

The stimulus however counterintuitively stipulates that Ebola is necessary for hiccups ("a symptom of no known disease except"). The stimulus also states that Ebola causes hiccups in many victims. The two stipulations illustrate a rather surprising fact that causal and conditional relationships can flow in the opposite (!) directions between the two phenomena:

hiccups --> Ebola

Ebola --c--> hiccups (in most victims)

(B) stipulates that

Ebola --some--> /hiccups

There is no way to come up with this breakdown under time pressure, but it's worth getting to the bottom of it on a blind review.

I don't see any issues with the question. Here's my proof that all vacuum tubes are not in fact preferable, regardless of heat resistance.

i) Let's take the whole superset of vacuum tubes; ii) Let's take ANY one and assume that it's preferable (for whatever reason, known or unknown to us); iii) two things follow: a. this tube's maximum current capacity is not comparable (because every vacuum tube has this property) b. this tube is comparable to semiconductors in all significant respects, such as maximum current capacity (because all preferable components must satisfy that necessary condition); iv) a. and b. contradict each other, therefore our initial assumption that the tube is preferable was wrong, therefore it is NOT preferable v) we picked a random (ANY) vacuum tube at the beginning, so the conclusion applies to every one in the superset (we can repeat this sequence of reasoning for every vacuum tube in the set).

In plain English: there are no preferable vacuum tubes in the superset, because any preferable would fail the necessary condition of being comparable to semiconductors on maximum current capacity.

tldr; the claims in the premises are so strong, they govern things that we are not explicitly said.

tl;dr: no contrapositives for "most"'

Google's Gemini has supplied a perfect illustration:

- The Premise (True): Most iPhones are black.

- The Inference: "If a phone is not black, it is probably not an iPhone."

If you walk into an Apple store and look at all the phones  that are not black, what are they? They are all iPhones. The probability that a non-black phone in that store is "not an iPhone" is 0%.

The video makes a great point on (E) which is somehow absent in the text version: "We know that all antibiotics now on the market, a vast subset of antibiotics, don’t fall within the exception, which means they have to follow the rule. What antibiotic are we talking about here?" (E) evades the rule through remarkably subtle language: "antibiotics that have been used."

Very educational dissection, thank you. Couple of observations: 1/ this long sentence appears to have lost its verb along the way: "Just because we now know that storytelling appears to be a universal aspect of culture and language does not the storytellers themselves have known it all along, especially not those from distant epochs." 2/ it may be worth highlighting that "all of the world’s cultures" in (C) seems to directly correspond to "a universal aspect of both past and present cultures" in the stimulus (all of the world’s literally means universal).

@JackVassau "[things that] should be provided, then..." is the necessary condition for the "things necessary for human health", not for the "primary purpose" condition. Just like B is not a necessary condition for C in A -> B -> C. Note that it reads if A, then if (!) B, then C.

When we kick "things necessary for human health" up to the domain, "then" before "[things that] should be provided" is removed along with the starting "if", just like "then" will be removed before B if we kick A up into the domain and are left with B -> C (if B, then C).

"So such wounds is a reference to deep wounds free of bacteria." (0:50 mark in the video) is a false statement. "Such wounds" refers to "deep wounds".

If we swap out the referential in the second sentence by the referent as suggested in the video, the resulting sentence will make no sense: "Even strong antibiotics failed to kill the bacteria that live in deep wounds free of bacteria."