Question

一个英文句子语法,第2句是对的，为什么？

Before signing up for next year's courses,《the students' schedules must be approved by their advisers.》

Before signing up for next year's courses,《the students must have their schedule approved by their advisers.》

正确答案是第2句，请问为什么。
我觉得第1句，我的理由是被证实，所以must be approved ，是被动句子，但为什么错呢。

麻烦讲解下。

Answer 1

换成下面两句看看吧

before you signed up for next year's courses,your schedules must be approved by their advisers.

before you signed up for next year's courses,you must have your schedule approved by your advisers.

这样就很容易看到了
第一句单独看前后半句是没有错的，但结合起来看前后主语不一致，前半句说你怎样怎样，后半句说你的课程表怎样怎样，不连贯，也不符合一般人的说法，所以错
第二句前后都是you做主语

Answer 2

因为主语应该是students 而不是student's schedule
signing up for the next year's courses是students的动作

Answer 3

意思正确不一定句子就正确。
此两句的关键是语法。
从句动词的使动者必须一致，或者说sign up 这个动作只有人才可以实施。

所以第二句才是正确的。