【题目】It wasn't easy having my friends talk about their freshman years____ I wasn't a part of.
A.whom
B.when
C.that
D.what

【答案】C
【解析】考查定语从句。本句先行词是their freshman years，这是指时间的名词，排除A项，因为A项指人；定语从句wasn'ta part of中介词of的后面缺少宾语，可知使用关系代词BCD中只有C项是关系代词。故C正确。