一道high gmat的疑问

tigercsh

错误选项：both sides are doing sth for each other
正确选项：each sides is doing sth for the other
解释只说了both 和　the other 不能搭配，为什么不能和each other 搭配？
谢谢

1stzhang

这个题目考察地就是逻辑意思地合理性。both sides are doing sth for each other说明自己还要给自己doing，有些象than any other city把自己必须排除在外。