Self-study
Support A number of seriously interested amateur astronomers have tested the new Exodus refractor telescope. ████ ███ ████ ████ ████ ██ ███████ ██ █████ ██████ █████████ ████████ ████ ████ ████ ████ ██ █████ ██████ ██ █████ ██████ ██████████████ ██████████████ █████████ ███████████ ████ ██████ ███ ██████ ███████████ ████ █████ █████ ██████████ ██████ ████ █████ ████ ███ ██████ ██████████████ ██████████████ ███████ █████ █████ ███████ ██████████████ █████████████ █████████ ███ ███████ ███████ ██████████ █████ ██ ██████ ███ ██████ ██ ███ ██ ██ ██ ██████ █ █████████ ███ █████████ ████████████
Argument Summary
The stimulus tells us that "a number" of "seriously interested amateur astronomers" have tried this new Exodus telescope. We're told that compared to the old Newtonian telescopes, the Exodus telescopes have allowed astronomers to see planetary features in much greater detail, despite gathering less light. The argument concludes that, based on these astronomers' experiences, other serious amateur astronomers who want a telescope for planetary observation should choose the Exodus telescope.
Analysis: Method of Reasoning
We're told that some people who fit a certain description ("seriously interested amateur astronomers") have tried a new item and have discovered some advantages it provides for a particular purpose: planetary observation. The argument concludes with the suggestion that everyone who fits that description — "any" serious amateur astronomers — and has the same goal should buy the new item.
21.
Which one of the following ████ █████████ ███████ ███ █████████
a
Telescopes of certain █████ ████ ███ ███████ ████ ██████ ████ ████ ████ █████████ ███████████ █ ████████ ██████████ █████████ █████████
Incorrect. We don't know whether these "certain types" of telescopes include the Exodus telescopes — or the Newtonian telescopes, for that matter. Since we don't know if (A) even applies to any of the telescopes in the argument, we can't say that it weakens the argument.
b
Image quality is ████ ███ ██ ███████ █████████ ███████ █████ █████ █████████ ██████ █████████ ███ ██████ ██ █ █████████ ███ █████████ ████████████
Correct. Remember that the only way we're told the Exodus outperforms the Newtonian telescope is in providing a clearer image of certain planetary features. This fact alone is the basis for the argument's recommendation that "any" serious amateur astronomer should choose the Exodus for "planetary observation." But if (B) is true, and choosing a telescope for planetary observation should consider other factors besides image quality, then the recommendation to choose the Exodus carries much less force, because we don't know how the Exodus performs in those other areas.
c
Many serious amateur ███████████ ████ ██ █████████ ██ ██████ █ █████████ ███ █████████ ████████████
Irrelevant. The recommendation in the conclusion is specifically for serious amateur astronomers who are "buying a telescope for planetary observation." We're not interested in those astronomers who aren't interested in doing so, regardless of how many of these there are.
d
The comparisons made ██ ███ ███████ ███████████ ████ █████ ██ ████████████ ████ ██████ ███████ █████████ ███████████ █████████
Irrelevant. Just because the astronomers' observations were made in several different sessions doesn't mean their observations aren't reliable, or that the recommendation based on their observations isn't worth following. (D) doesn't weaken.
e
The substance used ██ ████ ███ ██████ ██ ██████ ██████████ ███████ ████ ████ ████ ██ ███ ██████ ██ █████ ███████████
Incorrect. If the Exodus's lenses are made with a different substance than all other telescopes' lenses, this might just explain why the Exodus provides a better image than other telescopes. So (E) doesn't weaken the recommendation to choose the Exodus.