Official answers:
1. B
A: The similarity is only mentioned in passing. Not the primary objective. C: The author of the passage is not 'evaluating' the studies – he is just reporting them. D: This is mentioned as a future direction at the end of the passage. Not the primary purpose. E: No 'explanations' are offered.
2. D
The research group at Harvard Medical School showed that, like the zebra fish, humans too generate new heart cells from pre-existing ones. So they would agree with what is mentioned in options A, B and E. The researchers have not disputed the fact that stem cells are capable of self-renewal and are capable of becoming any type of heart cells.Their finding is only that while stem cells may be capable of doing this, they do not do this in humans. (So option C is wrong) This is contrary to the idea that stem cells are responsible for self-renewal of the human heart (lines 20-21). Option D says exactly this, and is the right answer.
3. C
Line 5 gives us a clue to the right answer: “Somewhat surprisingly, nuclear bomb tests during the Cold War had made this discovery possible” The surprise is directed at the fact that a discovery about a physiological phenomenon was made possible through something quite unrelated. i.e. a nuclear bomb test. All answer options except C mention extra information related to the method and findings of the study, whereas C talks about something about how the discovery was made. Option C makes inherent sense, and is thus the right answer
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Keep it simple. Keep it blank