题目内容：

1.Mr.Smith has _____ a bank clerk for five years.
A.be B.got C.become D.been
2.I think the best way _____ learn English is to use it as often as possible.
A.for B .of C.on D .to
3.They have been friends ______ they met at school
A.when B.until C.since D.before
4.我已经决定要离开了.
I have _____ _____ leave.
最好说下理由,为什么是这个

优质解答

1、D 这个是现在完成时的基本用法,has/have been在这里表示成为、是
2、D由learn是动词原形确定系动词用to
3、C have been现在完成时,有since的一般都是现在完成时
4、decided to