题目内容：

She had three sons,all___became doctors.
a.of which
b.which
c.of whom
d.who
请问这题是考什么知识点的?要选择哪一项?请说明原因,谢谢!
那主语是she谓语是had宾语是？all___became doctors在句中是充当宾语吗？

优质解答

答案:C.考定语从句.先行词“threesons”表人,所以后面宾语选whom,又因为是三者,所以是allofwhom