The first sentence of the stem would make a good SC question; it sounds like they declared for three weeks that the person was missing, but they mean to say that they declared that the person had gone missing three weeks earlier.
There's no way to answer this question without knowing what the stem is saying, and I have no idea what they mean when they say the man was "discovered in a state similar to hibernation". The only thing we know about hibernation, from the stem, is that it is characterized by slower breathing, lower body temperature, and a slower metabolism. When the person was found in a "state similar to hibernation", what does that mean? I can only conclude that his breathing was slower than normal, his body temperature was lower than normal, and his metabolism was slower than normal. There's nothing else "the man was discovered... in a state similar to hibernation" could mean, from the information in the stem. And if that's true, answer B is useless to us, because we must already know about his temperature, breathing and metabolism if we know he was in a hibernation-like state. Answer B essentially just restates a premise, so it wouldn't give us new information that would help us establish the conclusion.
The only answer I find justifiable here is D. It's also unclear to me what the stem means when it says "humans don't normally hibernate". If by that they mean "it is unknown if humans are capable of hibernating" (or if they mean what is actually true in reality, that there is no evidence that humans can hibernate), then answer D becomes a good answer. We have two competing hypotheses upon discovering this person in the snow. Maybe he was genuinely hibernating for a few weeks, or maybe he was just asleep. If we learned by experimenting on other people that humans were incapable of hibernating, then that would make it very unlikely this person was, because hibernating is one of those things that a whole species either does or doesn't do. But if we learned by experimenting that people can indeed hibernate, then that would mean that the hypothesis that this person was at least has a chance of being true.
The writing in the stem isn't clear enough for any one answer to be clearly correct, in any case. I found the original source of the question online, and the source claims the answer is B, but the logic of the "official explanation" is wrong (it ignores one of the central premises of the stem), so I don't think the question makes sense.