Unit 2 What is happiness to you?
a. sat b. had sat c. had been sitting d. was sitting answers: cacd4. 一般過去時和過去進行時的區(qū)別 1). 一般過去時表示在過去某時發(fā)生的動作或存在的狀態(tài)（包括過去習慣動作），常與just now, a moment ago, yesterday, last week(month, year), the day before yesterday及表示過去的時間狀語從句。如i was sixteen years old last year. he worked in a factory in 1986. i met her in the street the day before yesterday. he often swam in the river when he was young.2). 過去進行時表示過去某一段時間或某一時刻正在進行的動作。常與之連用的時間狀語有，at that time/moment, (at) this time yesterday (last night/ sunday/week…), at+點鐘+yesterday (last night / sunday…)，when sb. did sth等時間狀語從句。
eg. what were you doing at seven p.m. yesterday?
i first met mary three years ago. she was working at a radio shop at the time.
i was cooking when she knocked at the door.3). 一般過去時往往表示某一動作已經(jīng)完成，而過去 進行時卻表示動作在持續(xù)或未完成。
i saw you while you were speaking to joan.注意：有的過去時間狀語既可用于一般過去時，也可用于過去進行時，但含義不同。如： she wrote a letter to her friend last night.
她昨晚給她的朋友寫了封信。(信寫完了)
she was writing a letter to her friend last night.
她昨晚一直在給她的朋友寫信.（信不一定寫完）4). 過去進行時的時間狀語從句
(1). when 和while引導的狀語從句
while表示一段時間，因此它所引導的狀語從句中，謂語動詞常用進行時態(tài)，如：
when/while we were having supper, the light went out.(2). when用作并列連詞時，表示主句動作發(fā)生的過程中，另一個意想不到的動作發(fā)生了。
i was walking in the street when someone called me.
我正在街上走時突然有人喊我5.過去完成時1)在某一過去時間以前或過去某事之前已發(fā)生并完成的動作。by the end of last month they had treated 3,000 patients.by the time she competed in the new york goodwill games, she had been a dedicated junior gymnast for eleven years.2)表示一種未實現(xiàn)的愿望和想法。i had hoped to go on monday, but i couldn’t get away.i had thought that he was our english teacher.3)用與hardly…when, scarcely…when, no sooner…than句型中。hardly had he finished his homework when we went home.6. 過去完成時與一般過去時1). 歷史事實通常用一般過去時表示，如：
they learned that lincoln led the american war.
he told the students that hitler killed millions of jews.