【题目】His parents were teachers in that school, _______ lost their lives in order to save
their students in the earthquake.
A.none of them
B.both of them
C.none of whom
D.both of whom

【答案】D
【解析】经过分析，可知这个句子中包含一个非限制性定语从句。them不能引导定语从句，又因为his parents是两个人，表示两者故用both。