Hi Lawyered,
Thanks for your question!
The PowerScore staff has copies of all the tests, so you don't need to go to the trouble of re-typing the full question and answer choices.
I'll start by addressing your question about why answer choice (A) was incorrect. The argument in the stimulus is about finding "life as we know it." The stimulus uses this exact phrase multiple times, including in the conclusion -- "This indicates that the astronomer's model is wrong, and
life as we know it exists only on the planet Earth." Answer choice (A) states that forms of life
other than life as we know it exist on other planets. That makes it an incorrect answer choice. I know this may seem like an overly-fine distinction, but it's important to note the exact word choices used in an argument to be certain that the stimulus and the answer choices are talking about the same thing. Here, there's an important difference between "life as we know it" on Earth (perhaps mammals, trees, water) and "forms of life other than life as we know it" (sentient bacteria? frozen microbes? etc).
Answer choice (C) is correct because it offers a reason for why astronomers might have searched for planets with life as we know if outside of our solar system and failed to find it -- the reason being that we don't have instruments strong enough to detect life millions of light years away! For example, there might be "life as we know it" in the next solar system over, but if we don't have strong enough telescopes to observe that life, this would simultaneously explain (1) why we haven't found such life yet and (2) why the astronomer's model is actually correct.
It's ok that answer choice (C) adds new information, since the prompt asks us which of the following facts,
if accepted by the speaker, would make him reconsider his position. This implies that a new fact will be thrown in.
Answer choice (E) is incorrect because it doesn't address the failure of astronomers on earth to find extraterrestrial life. The astronomer's model doesn't depend on extraterrestrials contacting Earth, it depends on scientists on our own planet finding aliens abroad. Even if answer choice (E) were true, it wouldn't relate to the argument about the 1960 astronomical model being correct or incorrect.
I hope this helps clear things up. Good luck studying!
Athena Dalton