-- By the end of last month,Bruce _______ here for four years.

题目

-- By the end of last month,Bruce _______ here for four years.
-- No wonder he can speak Chinese so well.
A.worked
B.has worked
C.had worked
D.has been working
我知道是用完成时,但为什么选C不选B?

答案

题中Bruce是在上个月末为止,上个月是过去的时间,而Bruce的动作一直持续到过去时间,属于过去的过去,故用过去完成时.若题目将时间改为现在now,则可以选择B选项.