关于英语的一道选择题I'vestudiedinthisschool.AsincethreeyearsBbeforethreeyearsCsincethreeyearsagoDforthreeyearsago这道题目我只知道since后加时间点或者从句,for后面是加一段时间.但

Question

关于英语的一道选择题
I've studied in this school____.
A since three years B before three years
C since three years ago D for three years ago
这道题目我只知道since后加时间点或者从句,for后面是加一段时间.但是我不知道before的用法,是不是看到before也应该用完成时?
这道题目应该怎样分析?那个since+...ago的选项应该是归属现在完成时还是过去式?谢谢了!

Answer 1

应该选C
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).
I have been here since 1989.

2) since +一段时间+ ago
I have been here since five months ago.
before表示从过去或将来某一时间算起多少时间以前,由于与这一时间状语连用的行为先发生在过去或将来某一时刻之前,因此往往出现在过去完成时态或将来完成时态中.例如：
① I called him up last night, but his mother told me he had left for Wuhan two days before.
② She said that she had married him five years before.