请看下面的题，答句是个什么从句?
“What were you trying to prove to the police?” “_________ I was last night.”
A. That B. When C. Where D. What
【分析】此题应选 C，其余三项均有可能误选，答句为省略句，其完整形式为 I was trying to prove to the police where I was last night. (where 引导的是一个宾语从句)。请看以下类似试题：
(1) “What made her so happy?” “_________ her son passed the college entrance examinations.”
A. That B. 不填 C. Since D. For
【分析】此题选A，为That her son passed the college entrance examinations made her so happy. 之省略。
(2) “What did she tell you?” “_________ she would be late”
A. That B. When C. Where D. Whether
【分析】此题选A，为 She told me that would be late. 之省略。
(3) “What did he ask you?” “_________ I would be late.”
A. That B. When C. Where D. Whether
【分析】此题选D，为 He asked me whether I would be late. 之省略。
类似地，下面一句是非谓语动词作主语：
(4) “What made you so upset?” “_________ my wallet.”
A. Lost B. Losing C. Having lost D. Being lost
【分析】此题选B，为 Losing my wallet made me so upset. 之省略。
