选用since或for填空

题目

选用since或for填空
1.We have learned five lessons ____ the beginning of this term.
2.Mrs Liao has been in hospital ____ last week.
3.I have stayed at my aunt's ____ two weeks.
4.He has studied very hard ____ he came to our school.
5.We've been waiting ____ 20 minutes.

答案

1.since
2.since
3.for
4.since
5.for