When about his school life Tim thought it colorful.A. askedB. askingC. to askD. asks

问题补充：

When about his school life, Tim thought it colorful.

A. asked

B. asking

C. to ask

D. asks

答案：

(答案→)A. asked

B. asking

C. to ask

D. asks

解析：A考察状语从句的省略。当中状语从句的主语和主句的主语一致的时候，可以把状语从句的主语和be动词一起省略。本句ask与Tim之间存在动宾关系，所以使用过去分词的形式，在when后面省略了he was。故A正确。