BipashaAmin wrote:
Can anyone help me to understand the 2nd question, please? it seems that the answer choice B is correct. I have been thinking why C is correct and it seems ok to be the right answer but I just can't understand why B is not the correct one. Because to me, it feels like quasar and gamma rays were plausible position for the cosmic ray's source and the last line was contradictory to this explanation for the source of those cosmic rays. I just can't find my mistake.
Venomous passage
Analyzing it as the following:
X (Supernovas) are composed by \(x_1,x_2,\) ......so forth x-rays type
Supernovas in the Milky Way are the likeliest source
for most of the cosmic rays reaching Earth.
However, calculations show that
supernovas cannot produce ultrahigh-energy cosmic rays (UHECRs), which have energies exceeding 1018 electron volts. It would
seem sensible to seek the source of these in the universe’s most conspicuous energy factories: quasars and gamma-ray bursts billions of light-years away from Earth.
However, our X does not produce a CERTAIN type of rays which can not reach our planet BECAUSE 20% of those rays are lost every 20 millions of years. In 100 million light-years they become zero, basically.
Therefore our conclusion is the following
Consequently, no cosmic ray traveling much beyond 100 million light-years can retain the energy observed in UHECRs.In the context of the author’s argument,
the last sentence performs which of the following functions?
A) It explains a criterion that was employed earlier in the argument.
No. It is a conclusion not an explanation. it is the result
B) It shows that an apparently plausible position is actually self-contradictory.
It does not contradict anything before
C) It is a conclusion drawn in the course of refuting a potential explanation.
Yes. It is. Our potential explanation is that some other source is the origin of our rays. And the last sentence concludes that the rays from supernovas can not reach or pass over 100. The explanation is the match calculation above
D) It overturns an assumption on which an opposing position depends.
Nothing here is assumed
E) It states the main conclusion that the author is seeking to establish
The author does not establish anything. We have specific facts. Basically E says that we have an assumption but we do not. D and E says the same thing
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