有的定语从句考题为了增加难度和试题的灵活性，通常将定语从句与并列句结合起来考查，此时同学们要特别注意句中是否有并列连词and, but等。比较：

(1) He has two children, and both of ________ are abroad.

A. them                B. which                C. whom               D. who

(2) He has two children, both of ________ are abroad.

A. them                B. which               C. whom               D. who

第(1)题选A，第(2)题选C。由于第(1)题中用了并列连词and，从而使整个句子为并列句，and后应是一个独立的简单句，所以选A不选C；第(2)题没有并列连词and，both of whom are abroad为非限制性定语从句。另外，请比较下面一题，由于空格的没有谓语动词，而只有非谓语动词being，所以答案选A(逗号后为独立主格结构)：

He has two children, both of ________ being abroad.

A. them                B. which               C. whom               D. who