时间状语从句的时态

Question

我对时间状语从句中的时态问题已经搞乱了 请高人详细解答一下下面几道题as my father ........(leave)the house ,the postman.......(arrive)tom........(work)in the garden while i .........(sit)in the sun as i .........(walk)down the street,i...........(met)charliewhiile he ........(read)the letter,he ............(hear)a knock at the doorwhile mother..........(prepare)lunch, janet............(set)the tableshe ........(drop) the tray when i.............(speak) to her请详细解答一下为什么用

Answer 1

1. As my father was leaving the house ,the postman arrived.2. Tom was working in the garden while i was sitting in the sun 3. As i was walking down the street,i met charlie4. Whiile he was reading the letter,he heard a knock at the door5. While mother was preparing lunch, janet was setting the table6. she dropped the tray when i was speaking to her这几个句子实际上是考查when， while和as引导时间状语从句的区别。如果从句动作是主句动作发生的背景，从句用进行时态表示动作发生的背景，主句用一般过去时，此时三者可以互换；如果表示“一边..., 一边...”只能用as；表示两个动作同时进行，主从句都用进行时，此时只能用while；如果主句是从句谓语动作的背景，主句用进行时，从句用一般过去时，此时只能用when。