一般過去時(shí)
　　1.基本用法
　�。�1）常用來表示過去某一時(shí)間所發(fā)生的動(dòng)作。
　�。�2）表示在過去一段時(shí)間內(nèi)經(jīng)常發(fā)生的動(dòng)作或存在的狀態(tài)。
　　2.基本結(jié)構(gòu)
　　(1)主+be動(dòng)詞(was/were)+名（代/介詞短語）
　�。�2）主+動(dòng)詞的過去式+賓
　　(3)動(dòng)詞的過去時(shí)變化（略）和含過去時(shí)句子的肯定、否定、疑問變化。
　　did, didn’t, Did...?
　　e.g.Where were you at that time?
　　I was sorry to hear that.
　　Who left the door open?
　　What did you major in?
　　Did you go home yesterday? Yes, I did. No, I didn’t.
　　I didn’t go home yesterday.
　　3.過去時(shí)的句子常帶有標(biāo)志性的時(shí)間狀語
　　...yesterday, at that time
　　...ago, last year, week, just now etc.
　　4.Ago
　　(1)多用于過去時(shí)。
　�。�2）它所指時(shí)間是從現(xiàn)在算起。
　　It was  20 years ago when Jack was a boy of fifteen.
　　5.Before
　　(1)多用于過去完成時(shí)
　　（2）它所指時(shí)間是從過去某一時(shí)刻算起（可與previously換用）。
　　Last summer, I finally left the firm that I had joined 18 years before.