偶看新闻甲醇泄露什么症状:情态动词--ought
来源：百度文库 编辑：偶看新闻 时间：2024/04/28 17:05:35
九.情态动词--ought
ought只有一种形式，后面须跟带to的动词不定式。Ought表示"有义务或必要"做某件事，还可表示"劝告"。如：.You ought to follow the old man's advice.你应当听那位老人的话。
You oughtn't to smoke so much.你不应当抽烟太多。
You ought to go to the clinic at once. You don't look well.你脸色不好，应该马上到医务室去。
[注]ought表示"应该"，语气比should 强。
ought后加动词不定式的完成式时
指过去的动作。如用肯定形式(ought to have done)，表示某一件事该做而未做，相当于should have done。如用否定形式(ought not to have done)，则表示一件不该做的事情发生了，相当于should not have done。如：
He ought to have done the exercise more carefully.这个练习他应当作得更细心一些。
I ought to have returned these books to the library last week. 我上星期就应当把这些书还给图书馆。
You ought not to have been so rude.你不该这样粗鲁。
You ought not to have taken his skates without asking him.你不该没有得到他的许可就把他的冰鞋拿走。
十.情态动词--dare
dare的用法和其他动词有所不同。dare用于否定句或疑问句中时，其用法和其他情态动词一样，即dare本身无变化，后面所跟的动词不定式不带to。如：They dare not tell the truth.他们不敢说真话。
Dare he admit his mistake? 他敢于承认错误吗?
He dared say no more。他不敢再说了。
但是dare用在肯定结构中时，后面的动词不定式可加to。如：
Young people should dare to think，dare to speak and dare to act.青年人要敢想、敢说、敢干。
[注一]在否定句或疑问句中，dare也可用作实义动词，用助动词do来帮助，后面的动词不定式可带to。如：
Do they dare to do it? 他们敢做这事吗?
The enemy did not dare to come out after dark.敌人夜间不敢出来。
[注二]注意下面将两种不同动词揉合在一起的说法。如：
I didn't dale come.我不敢来。
Who dares stop me? 谁敢阻拦我?
十一.情态动词--need
need的用法与dare几乎完全相同。即在否定句或疑问句中，和其他情态动词一样，本身无变化，后面用不带to的动词不定式；在肯定句中时，和实义动词一样，后面的动词不定式要带to，第三人称单数现在一般时加-s，并有时态的变化。如：Need we return the magazines today?我们今天需要把杂志还回去吗?
Every member needs to pay only a little money a year to get medical care.每个成员每年只需缴一点钱就可以得到医疗。
You need not write down your translation. You may do it orally. 你们不必写下这个翻译练习，口头做就行了。
[注]与dare一样，在否定句或疑问句里，need也可和实义动词相同，用助动词to do来帮助，后面的动词不定式必须带to。如：
Do they need to take any tools with them? －No., they don't need to.他们需要带工具吗? --不需要。
He did not need to go there early that day. 那天他不必早去。
need后面有名词作宾语时
完全用作实义动词，表示"需要"或"缺乏"某件事物。这时，它的变化和一般实义动词完全相同。如：
I need a dictionary.我需要字典。
You need a hair-cut. 你该理发了。
Do you need a fountain-pen? 你需要一支自来水笔吗?
I don't need a new jacket. 我不需要一件新茄克衫。
Mary looks tried，she needs a rest. 玛丽看上去累了，需要休息。
Needn't后加动词不定式(不带to)的完成式时
指过去已做了但勿须做的动作。如：
You needn't have watered the vegetables，as it is going to rain.你满可以不必浇菜，天要下雨了。
You needn't have brought your umbrella. We are going by taxi你满可以不必带伞，我们要坐出租汽车去。
[注一]注意didn't have to和didn't nee to则常表示过去未做也勿须做的动作。如：
I didn't have to interpret it for her，for she knows Chinese.我勿须为她翻译，她懂汉语。
I didn't need to take a taxi； it is only five minutes walk to the station.到车站只须走五分钟，我不需要坐出租汽车。
[注二] used to和had better也可看作是情态动词。情态动词used to表示过去的习惯，但现在已无此习惯(would表过去习惯时则无此含义)。如：
When I was young，I used to play football.我小时常踢足球。
He didn't use to come. (或用usedn't to)他过去不常来。
Did he used to come? (亦可说used he to...?)他过去常来吗?had better表可取，意为"应该"或"最好"。如：
We had better go now. 我们最好走吧。
You'd better stop now.你现在应该停下来。(对长辈不可用had better)
Hadn't we better go now? 我们现在走不好吗?(had better一般不用于肯定疑问句)