Smith wrote an article on he failed to pass the exam.A. whyB. thatC. whoD. what

问题补充：

Smith wrote an article on he failed to pass the exam.

A. why

B. that

C. who

D. what

答案：

(答案→)A. why

B. that

C. who

D. what

解析：考查宾语从句。On是介词，后面接宾语从句，宾语从句的句子结构很完整，使用连接副词。排除CD。因为CD的连接代词，在句中做主语，宾语，表语，故A正确。句意：斯密斯写了一封信，关于为什么他没有通过这次考试。故A正确。