On the bus I saw a student I thought was your brother.A. whoB. whomC. whichD. /

问题补充：

On the bus I saw a student I thought was your brother.

A. who

B. whom

C. which

D. /

答案：

(答案→)A. who

B. whom

C. which

D. /

解析：考查定语从句，先行词是a student，定语从句中I thought是插入语，所以定语从句缺少主语，句意：在公共汽车上我看见以为是你哥哥的一个学生。选A。