英语现在完成时态专项练习,写出答案并说为什么

题目

英语现在完成时态专项练习,写出答案并说为什么
--When____he____(go) there?
--He____(go)there to study chemistry in 1945.He____(not return) until 1951.Last year he____（go) there again to attend an important meeting.

答案

--When( did ) he (go) there?
--He (went )there to study chemistry in 1945.He (didn't return) until 1951.Last year he （went ) there again to attend an important meeting.
注：以上句子都是一般过去时,因为都有明确的过去时间状语.
加油!不明白再问!