EX15. Chuyển các câu sau từ thì hiện tại hoàn thành sang thì quá khứ đơn sao cho nghĩa của câu không thay đổi. 1. We have learned English for 10 years. => ____________________________________________________________________. 2. It has been a long time since we last met. => ____________________________________________________________________. 3. Ms. Ann hasn’t taken part in any voluntary programs for 4 years. => ____________________________________________________________________. 4. I haven’t mer my family since last Christmas. => ____________________________________________________________________. 5. How long have you lived here? => __________________________________________________________________ 6. The volunteers have provided free food and fresh water to homeless people since yesterday. => ____________________________________________________________________. 7. The doctor has quitted his job in the local hospital and moved to the central hospital for 2 days. => ____________________________________________________________________. 8. The children haven’t had a long vacation since last year. => ____________________________________________________________________. 9. They haven’t visited their parents for 3 months. => ____________________________________________________________________. 10. It has been 2 years since we broke up. => ____________________________________________________________________.