--------the age of twenty,he had written two books.A.At B.On C.By D.from

题目

--------the age of twenty,he had written two books.A.At B.On C.By D.from
其中该选哪个呢?
要说明理由哦~

答案

C.By
by the age of 截止...岁；到……年龄时
这个时间状语一般用于过去完成时,后半句had written ,所以选C