8.We have eaten since it started to rain.
(S + started / began + V_ing / to-V = S + have P.P / have been + V_ing : bắt đầu làm việc gì)
9.I haven't cut my hair since I left her.
(S + last + V_ed + time+ ago : lần cuối cùng làm gì = S + have/ has +not+ for/since + time)