Unit 5 重点语法
教学目标：掌握过去进行时的用法及跟一般过去时的区别
掌握when和while用法及区别
1. 过去进行时
( 1 ) 过去进行时的用法。
过去进行时表示过去某一时刻或某一段时间内正在进行或发生的动作，由“was / were + 现在分词”构成。
现以动词wor为例，其肯定式、否定式和疑问句式见下表：
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肯定式 |
否定式 |
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I/ He / She was woring. We/ You/ They were woring. |
I / He / It was not woring. We / You / They were not woring. |
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|
疑问式和简略回答 |
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Was I woring? Yes, you were. No, you were not. |
Were you woring? Yes, I was. No, I wasn’t |
Was he/ she/ it woring? Yes, he/ she/ it was. No, he/ she/ it wasn’t. |
|
Were we/ you/ they woring? Yes, you/ we/ they were. No, you/ we/ they weren’t. |
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表示过去进行时的时间状语有：at that time, this time yesterday, at ten yesterday evening, from eight to twelve yesterday 以及when, while引导的时间状语从句。
It was raining at 6 o’cloc this morning.
What were you doing this time last night?
He was sleeping when the UFO arrived.
( 2 ) 与一般过去时的区别。
① 表示已完成的动作用一般过去时，未完成的动作则可用过去进行时。
I wrote a letter this morning.
I was writing a letter this morning.
② 一般过去时侧重于叙述事实，过去进行时则侧重于动作的持续性，从而更具描绘性。
It snowed last night. It’s all white outside now.
It was snowing last night, so it was very cold.
③ 两个动作同时发生时，较短的动作可用一般过去时，而较长时间的动作可以用过去进行时表示。
Mom was taling with Sue’s teacher when Sue entered the room.
2. When 与while的区别
When和while都可以引导时间状语从句，表示“当......时候”，但是二者之间又有区别。
( 1 ) when引导的时间状语从句中的动词可以是非延续性动词，也可以是延续性动词，而while从句中的动词必须是延续性动词。
I was watching TV when you called me.
It began to rain while we were waling in the par.
( 2 ) when说明从句动作和主句动作可同时发生，也可先后发生。而while强调主句动作在从句动作发生的过程中同时发生。
When the pot fell to pieces, the girl began to realie that she was not alone.
( 3 ) when或while引导的时间状语从句可以相互改写，但while引导的句子常用进行时态。
When they came in, the girl was dancing.
= While the girl was dancing, they came in.
( 4 ) while还可以做并列连词，意为“而，却”，表示“对比关系”，有轻微的转折之意。
She is very outgoing, while her sister is a little shy.
