I 肯定句和否定句中的情态动词

一、情态动词的现在式在肯定句中的比较

1. can表示体力或脑力方面的“能力”、“技能”或根据客观条件能做某种动作的“可能性”

1) Mild forms of execrise can some of the loss of flexibility that accompanies aging.

［A］ stop
［B］ to stop
［C］ stopping
［D］ be stopped

但表示人体力或智力的具体动作时须用 be able to

He was able to do that without any help.他不需要任何帮助就能完成这项工作。

2. may表示“允许，可以”，相当于be allowed to

2) If there is social or political change in a region ［A］ where a standard language ［B］ is spoken, local varieties ［C］ of the language may developing ［D］ .

may或might可和as well连用，表示“建议”，译为“还是……的为好”

You may as well keep a certain distance from that mad man. 你们还是离那疯子远点为好。

You might as well go home now.你还是现在回家为好。

3. must表示“必须”或“应当”、“一定”

3) The formation of snow must be occurring ［A］ slowly ［B］ ， in calm air， and at a temperature near ［C］ the freezing point ［D］ .

4. have to 加动词原形，表示“不得不”，“必须”，它比must更强调客观

Tom had to work into the deep night everyday to earn a living. 汤姆为了生计每天都得工作到深夜。

5. should 表示“劝告”，“建议”或“义务”时，译作“应当”，或表示“预测”和“可能”
He should take care of his parents as they are old enough not to live on themselves. 由于父母亲老了，不能自理，他应当照顾他们。

He should be there now. 他可能到了。

should have done在虚拟语气中表示“责备或后悔”［参见第三章第一节、二、2.］。

6. ought ，只有一种形式，即ought后必须加to，然后跟接动词原形表示“有义务”或“必要”做某事，译为“应当，应该”

4) The traditional goal of science is to discover how things are,not how they ought .

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