This is a weakening question: Which one of the following, if true, would cast doubt on the experimenters’ conclusion?
Our stimulus begins with a definition of nuclear fusion; nuclear fusion is a process where nuclei fuse and release energy. We then learn that this process creates a by-product; helium-4 gas. Having established this context, we now learn about an experiment involving “heavy” water. I don’t know about you, but I have no idea what “heavy” water is; luckily the LSAT is about our reasoning skills and not chemistry. We learn that the water is contained in a sealed flask within an air-filled chamber, and that after the experiment some Helium-4 was found in the chamber. The people running the experiment concluded that there must have been nuclear fusion that happened. Since this is a weakening question involving a hypothesis, we should look for an alternate hypothesis in the answer choices, an alternate possible explanation for why there was helium-4 in the chamber. Let’s see what we get:
Answer Choice (A) The researcher’s explanation is entirely compatible with this.
Answer Choice (B) But was it fusion that produced the helium-4?
Correct Answer Choice (C) We are told the chamber was air-filled, so we would therefore expect that level of helium-4. This is a much better explanation than that nuclear fusion occurred!
Answer Choice (D) But it was helium-4 they found. If anything this suggests the helium-4 was recently produced which might support the fusion hypothesis.
Answer Choice (E) Cool, but we weren’t told anything about heat; for all we know there was a large release of heat and our experiment runners hypothesis is entirely correct.