Carcass wrote:
Explanation
1) All three choices are correct. The question asks about claims the author would agree with. Choice A is correct: The passage states that supernovas in the Milky Way “cannot produce ultrahigh-energy cosmic rays.” Choice B is correct: Since very distant quasars and gamma-ray bursts are
“billions of light-years away from Earth,” they are too far away for a UHECR to reach Earth. Choice C is correct: The last sentence of the passage states that “no cosmic ray traveling much beyond 100 million light-years can retain the energy observed in UHECRs.”
2) The last sentence is the conclusion of an argument in the last half of the passage; it puts a constraint on the possible origin of UHECRs relative to Earth and thereby rules out the possibility, mentioned earlier in the passage, that distant quasars and gamma-ray bursts could be the origin of UHECRs. Therefore Choice C is correct. It is important to note that the last sentence does not show any plausible position to be self-contradictory (Choice B), and that it does not state the author’s main conclusion (Choice E), since it is relevant to only one of the two hypotheses considered in the passage.
The first question's third choice seems ambiguous as the passage points out
much beyond than 100 million light years, however, the answer choice (C) says
no more than 100 million light years. How that can be?
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45% (03:14) correct
