6. I ______________ her yesterday. (not see)
7. I _____________ her since yesterday. (not see)
8. My dad ______________ for this company 20 years ago. (work)
9. My dad ____________ for his company for 20 years.
10. Mai and Lan _______________ friends since they were in primary school. (be)
11. When I _______________(get) home last night, I ______________ (be) very tired.