Explain the answer

@Steph, Happy to help. The question asks us to select the answer that the author would consider to be least important in future research on neurogenesis in humans. This is a question where we can look for four answers that the author would consider important for research, and the answer that isn't nearly as important (or is irrelevant) will be our answer choice. Answers, C, D, and E can all quickly be eliminated, as there is textual support in the final paragraph that suggests the author would consider all of them to be important. Answer C is supported by line 57 (mention of neurogenesis in the young human brain). Answer D is supported by line 54 (mention of long-term memory). Answer E is supported by line 53 (mention of complex learning). All of this is discussed within the context of finding a mechanism that would enable the human brain to repair itself. Looking at answer A, it's supported by the beginning of the last paragraph where the author states that the findings of research on canaries might help uncover a mechanism that would enable the human brain to repair itself through neurogenesis. The implicit assumption here is that this would involve research comparing the brains of canaries with humans. Answer A is almost certainly something the author would consider important in future research, so we can get rid of it. That leaves us with answer B. This would by far be the answer that the author would consider least important for further research. The author's discussion on brain sizes in canaries changing is in the third paragraph, and the author says this might be partially due to canaries' requirements of flight (line 43). This would mean that a lower ratio of brain weight to body weight would be advantageous to the canaries for flying since they're carrying less mass. However, we know that humans don't fly, so this would not matter at all for us. The author would almost certainly view research on the ratio of brain weight to body weight to be totally irrelevant in future research on neurogenesis of humans. Does this make sense? Let us know if you have any more questions!

So basically you have to bring in outside knowledge?

Where do you think we need to bring in outside knowledge here? I think that we can (and Ravi did) explain how the author would find ACDE helpful in the passage, and I think that just within the four corners of the passage, we have a good argument as to why B would not be helpful: the ratio really only mattered as canaries need to fly, which humans do not.