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