(1) Since + S + 过去式，S + 现在完成式
例句：Since he went to senior high school, he has worked very hard.
自从他上高中，他一直很用功。
(2) It is +--- + since +持续性谓语动词(表否定)
例：It is three years since she lived here. 她已三年不住这儿了。
(3) It is + --- + since S + 瞬间谓语动词(表肯定)例：It is years since I stopped smoking).我戒烟已经数年了