Điền " for " hay " since " vào chỗ trống :
1. I have worked here ...... six years
2. I haven't seen him ......... several days
3. We've lived in the same house ...... 1995
4. I haven't smoked a cigarette ....... two days
5. They have been friends ..... high school
6.Loan's been sick .......... Wednesday
7. I have learnt English ............ I was in primary school
8. She has slept ........ more than ten hours