The head of the company promised to deal with matters of this sort----he returned to his office

题目

The head of the company promised to deal with matters of this sort----he returned to his office
A .until B.while C.by the time D.the moment
我想选C 想请问一下为什么 另外 the moment和 by the time 用法上有什么区别》》》谢谢!

答案

the moment 后面的从句的时态跟主句一致.而by the time 后的从句跟主句不一致.这题如果用by the time 前面要用 had promised.