The Whites have two sons and ---are studying in university.

问题描述:

The Whites have two sons and ---are studying in university.
A.two of them B.they all C.two D.the two of them
答案是D为什么啊,还有B为什么不行

因为总共就两个,所以用the two,如果总数多于两个则可以用A.
B的话,因为是两个,只能用both,多于两个才能用all.