Why is D incorrect?

@srodgers151 Happy to help! The question is asking for the answer choice that "MOST helps to explain the unexpected result." Although the logic in (D) may provide a plausible explanation, it is weakened by the use of the words "can" and "sometimes." These words imply that the phenomenon described in (D) is not always the case. In comparison to (C), which implies that plankton always utilize the nutrients released by organisms killed by viruses, (D) is not as strong. Therefore, (C) MOST helps explain the result and (D) can be eliminated. Does that make sense? Please let us know if you have any other questions!

That is really helpful actually. Is this strategy transferable to similar questions? By strategy I mean to look for answers that are logical and used stronger language - without hedging?

@srodgers151 Yes, I would recommend utilizing this approach as something to consider! Although it by itself is not necessarily a foolproof strategy and it depends on the type of question presented, it is generally wise to pay attention to if the language used is conditional or stronger. Best of luck with your studies and let us know if you have further questions!