lsat-20-3-21

21. Which one of the following most seriously weakens the argument? (A) Telescopes of certain types will not perform well unless they have been precisely collimated a delicate adjustment requiring deftness. (B) Image quality is only one of several different factors that, taken together, should determine the choice of a telescope for planetary observation.
(C) Many serious amateur astronomers have no intention of buying a telescope for planetary observation. (D) The comparisons made by the amateur astronomers were based on observations made during several different observation sessions. (E) The substance used to make the lenses of Exodus telescopes differs from that used in the lenses of other telescopes.

我选a 答案b  。我对这类题很头疼。今天第二个了。首先，b 有一定的削弱作用，只是提出一种可能。这种可能说 这种考虑 Image quality  只是一部分原因。但没有对比其他的部分，我们不能得到底两者比怎么样。其次，我认为，a 也提出了种可能的削弱。认为8-inch telescopes的 Image quality的问题是因为调试不当。我在这两种选择中不知道如何取舍，解这种题的方法如何，两个可能的答案？

Why B?: the thread of the reasoning in the stimulus is: Exodus can capture the details of certain picture where Newtonian can only obtain fuzzy images, therefore, any serious oberservers should choose Exodus rather than Newton.

---this reasoning indicates that the consideration of image quality is enough for making any decision on choosing a telescope.

B weakens the reasoning by arguing that image quality is not the only factor for making the decision.

Why not A?

For A to be able to weaken the argument, you have to assume that "8-inch telescopes的 Image quality的问题是因为调试不当". However, you are not supposed to make your own assumption for the statement to be able to weaken the argument. The correct answer always directly weakens the original argument.

great！！