一般过去时主要用来表示过去发生的动作或状态。常与表示过去的时间状语连用，如yesterday, last week, three years ago, in 1978, a moment ago, just now.

　　【例如】

　　After graduation, Sam worked in IBM as an engineer for a short period, and then he switched to Haier group.I was born in 1960sintosa humble family in countryside and I went to the college in 1979 after years of effort.He left the classroom a moment ago. He must have gone to the library.The last half of the 19th century____the steady improvement in the means of travel. (CET-4 1998, 6)

　　A) has witnessed

　　B) was witnessed

　　C) witnessed

　　D) is witnessed

　　由于谓语动词后面有宾语the steady improvement，谓语动词应为主动形式，另外，主语表明的时间是过去时间，故谓语动词用一般过去时，答案为C.* used to do sth.表示过去的习惯动作，现在不再做了。

　　【例如】

　　I used to go to work by bike. Now I go to work by taxi.