一道关于限定词语法的选择题

问题描述:

一道关于限定词语法的选择题
The students spent --- their time working in the fields.
A.both B.most C.more D.half
不确定B还是D,most their time也可以说的吧?都可以说most people ,most work,所以可以选B吗?D却好像也对.

虽然具体语法将不出来,但是凭预感的话most 后面还有their 的话肯定是要用most of their time.
所以这个题目应该选择D.half肯定对