If_ to look after lugguage for someone else,inform the police at once

题目

If_ to look after lugguage for someone else,inform the police at once
A asked B to ask.C asking.D having asked.如何判断!
通俗易懂一点

答案

A asked 这是带连词的过去分词 作状语 与句子主语（省略的you) 是被动关系 故用过去分词