Leaving behind family members, these farmers are strangers to the cities they work.A. in

Leaving behind family members, these farmers are strangers to the cities they work.
A. in that
B. at which
C. where
D. which

A. in thatB. at which(答案→)C. whereD. which解析：考查定语从句。先行词是cities,定语从句主语是they，谓语动词是work，是不及物动词，不需要宾语，故使用关系副词，先行词是cities，指地点，故使用where.C 正确。

就是这个解释