过去进行时：

　　在过去的某一点时间，或者是过去某一动作同时发生的另外一个动作

　　瞬间动词(arrive)无进行时态

　　I am arriving 进行时态表示将要

　　When he arrived,I was having dinner.

　　同时发生的两个动作，均用过去进行时

　　When I was doing my Homework,my mother was cooking.

　　When my mother was doing the housework,my father was watching TV.

　　同时发生的两个动作

　　1.一个用一般过去时，另一个用过去进行时

　　2.分工的情况，均用过去进行时

　　When the plane arrived,...were waiting inside the main building

　　while others were waiting on...

　　Two men took the parcel off...

　　take sth.off...=take sth.away from...

　　and carried it into...carried 表示看得很重

　　Customs House 海关

　　While...

　　...were keeping guard at the door,two others opened the parcel.

　　表面上是分工，两个动作同时开始，不是同时开始同时结束，延续时间不一致，

　　长一点时间的动作用进行时态，短时间的动作用过去时.

　　When someone knocked at the door,I was having dinner.

　　keep guard 守卫;at the door 在门边

　　two others=two other detectives

　　To their surprise

　　to one's surprise,让某人惊讶的是

　　To my surprise,the teacher was late.

　　to one's joy

　　To my joy, my mother came here yesterday.

　　to one's excitement

　　To our excitement,our team wins.

　　be full of ...装满

　　My bag was full of books.

　　The cup is full of water.