sinceafter的用法区别

问题描述

精选答案

since的时态必定是现在完成时和过去完成时：he has taught english since 2000.after后面加一段时间，时态是过去(完成)时，将来时：he will go to the underground station after ten oclock.

相关介绍：

since用法：

1）since+过去一个时间点（如具体的年、月、日期、钟点、1980，last month，half past six）。

2）since+一段时间+ago.

例如：I have been here since five months ago. 我在这儿，已经有五个月了。

3）since+从句。

例如：Great changes have taken place since you left. 你走后，变化可大了。

Great changes have taken place since we were here.我们走后，变化可大了。

4）It is+一段时间+since从句。

例如：It is two years since I became a postgraduate student. 我考上研究生有两年了。