2017年外研版必修一Module4 Period 3课时巩固提升含解析 【知识拓展】 (1)当从句谓语动词为非延续性动词时, 表示这段时间从该动作开始时计算, 即自从做……以来已经多久了。 (2)当从句谓语动词为延续性动词时, 表示这段时间从该动作结束时计算, 即自从不做……以来已经多久了。 ①It is two years since he joined the army. 他参军两年了。 ②It is two years since he was a soldier. 他退役两年了。 5. I bought this watch five years ago. (改为同义句) →I_______ _______ this watch for five years.