哦,突然想起来一点。。其实 选项B+选项C=each fraction has the same statitistical error, 选项C确保了the same(statitistical error),选项B确保了each (fraction)。 因为C只提到了rich和poor,而B确保了rich+poor=each。 -- by 会员 曳烛 (2012/3/18 11:54:36)
The above analysis is useless. The GMAT CR question asks you to find a SINGLE answer, not a combination of two.
B) is a sufficient assumption.
C) is a necessary assumtion.
B) + C) is still a sufficient assumption, not a necessary one. |