Example：
Whether the world is Euclidean or non-Euclidean is still an open question.
However， if a star's position is predicted based on non-Euclidean geometry，
then when a telescope is pointed toswheresthe star should be it will be ther
e. Whereas， if the star's position is predicted based on Euclidean geometry，
then when a telescope is pointed toswheresthe star should be it won't be th
ere. This strongly indicates that the world is non-Euclidean.
Which one of the following best expresses the main idea of the passage？
（A） The world may or may not be Euclidean.
（B） The world is probably non-Euclidean.
（C） The world is non-Euclidean.
（D） The world is Euclidean.
（E） The world is neither Euclidean nor non-Euclidean.
Choice （A） understates the main idea. Although the opening to the passage st
ates that we don't know whether the world is non-Euclidean， the author goes
on to give evidence that it is non-Euclidean. Choice （C） overstates the main
idea. The author doesn't say that the world is non-Euclidean， just that evi
dence strongly indicates that it is. In choice （B）， the word “probably” prop
erly limits the scope of the main idea， namely， that the world is probably n
on-Euclidean， but we can't yet state so definitively. The answer is （B）。
Premises
Once you've found the conclusion， most often everything else in the argument
will be either premises or “noise.” The premises provide evidence for the c
onclusion； they form the foundation or infrastructure upon which the conclus
ion depends. To determine whether a statement is a premise， ask yourself whe
ther it supports the conclusion. If so， it's a premise. Earlier we saw that
writers use certain words to flag conclusions； likewise writers use certain
words to flag premises. Following is a partial list of the most common premi
se indicators
责任编辑：sealion1986
