Why D is not the right answer...

@Karry-Jiao, Happy to help! Let's take a look at the argument before we look at the answer choices. M tells us that it's nearly impossible to find a left-handed person between the ages of 85 and 90. Q replies by pointing out that 70 to 90 years ago, kids were punished when they used their left hands and were forced to use their right hands. The question stem says, "Q's response serves to counter any use by M of the evidence about 85 to 90-year-olds in support of which one of the following hypotheses?" This question is kind of tricky, but once we realize that it's basically a cannot be true/must be false question, then it becomes much easier to tackle. What type of conclusion would M attempt to make that would not hold up based on Q's reply? Q's response gives us evidence that older people and their propensity to be right-handed is likely due to the environmental factors these people grew up with in being forced to use their right hands, which is why so few of them are lefties. This casts doubt on the possibility that the reason there are so few 85 to 90-year-old lefties is due to genetics or some other cause. You're asking about (D). (D) says, "Handedness is a product of both genetic predisposition and social pressures." The problem with (D) is that it does not make sense for M to draw this conclusion based on his evidence, and Q's response appears to go along with what this statement is saying, rather than go against it (which is what we need). Additionally, the stimulus doesn't delve into genetic predisposition, so we could not know either way whether or not this is true. Based on what you wrote, it sounds like you may have misinterpreted what the stimulus is telling us to do. The way the stimulus is worded, we're trying to pick an answer that, if we take Q's response to be true, would prevent M's statement from supporting something. The stimulus, with Q's response to M's statement, DOES NOT support a hypothesis about survival, and this is exactly why (A) is our answer. (A) says, "Being born right-handed confers a survival advantage." The reason this is the correct answer choice is because of M's reference of the ages of the people who are almost all right-handed (the 85 to 90-year-old group). Based on this evidence, it's reasonable that somebody could conclude that being right-handed confers some sort of survival advantage because such a high percentage of people 85 to 90 are right-handed and they're also all very old. However, when Q's response enters, Q's evidence pertaining to how people of that generation were raised and encouraged to be right-handed brings up a strong counter to the conclusion that being right-handed confers a survival advantage. If pretty much everyone in this age group was forced to be a righty anyway, what's to say that THAT's not the cause of there being such a high proportion of people 85 to 90 who are right-handed? (A) is a conclusion that, if we accept Q's response to M's statement, must be false, so this is the correct answer. Does this help? Let us know if you have any more questions!

Thanks very much for your detailed explanation! That's very helpful!

@Karry-Jiao, happy to help! Let us know if you have any other questions!