I have left for three hours.有无语法错误?

Since he left after I have been looking for living. I have left for three hours.有无语法错误? I have been working in this factory for about 20 years and seldom []so tired as now选择 A I have left B I had left C have I left D had I left I have few left 句中的left Father ____ for London on business upon my arrival,so I did not see him.A has left B left C was leC was left D have left I hear Mr Green ___ for New York last week.A.have left B.leaves C.leave D.left I can't wait for you _____minutes,any more,We have ____time left. For i have nothing left to be here on this earth today I will have left for America by the time he arrives这句怎么翻译? You have 3 credits left for today (what's this?)can I When the Penfriend you? Since he left after I have been looking for living.是什么意思? ( )2.I left home for England in 2002___ the first time.And I have been there___ three times.A.for,for B.for,/ C./,for D./,/ I ___ you ___ left for Shanghai.A.thought,had B.think,have C.think,had D.thought,have I ______ you _____ left for shanghai.A.thought,had B.think,have C.think,had,D.thought,have. 适当形式填空Oh,I _(leave) my pen in the classroom为什么用left而不用have left答案上是left,老师说是have left下面一句是Don`t worry.I_(get) it for you My parents have promised to come to see me before I -----for Africa.A.have left B.leave C .left D.will leave My parents have promised to come to see me before I _________ for Africa.A.have left B.leave C.left D.will leave 英语：my parents have promised to come to see me before i（）for AfricaA have left B leave C left D wll leave选哪个 为什么