情态动词should和will和need的用法详解解析
（1）should / ought to
①should和ought to表示应当、应该，前者比后者语气轻。如：
You should / ought to work hard.
②should / ought to的否定形式表示禁止之意。如：
Children shouldn’t smoke.
③should可表示陈述意见，推出建议或请求；而ought to可以表示劝告之意。如：
You ought to respect your parents.
He suggested that they should leave at once.
④should 可以用来表示说话者“吃惊”的语气，常翻译成“竟然”。
You can’t imagine such a well-dressed man should be so rude to a lady.
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（2）will / would①will 用于各种人称表示“意志”、“意愿”或“决心”等，否定式won’t + 动词。如：I will tell you all about it.Tom won’t do such a thing.②will用于疑问句中，常用在第二称时表示说话人向对方提出“请求”或“询问”如：Will you please tell her the news when you see her?③will 表示习惯性的动作，有“总是”、“惯于”的含义。如：Fish will die out of water.④would 表示客气的请求、建议或意愿。如：Would you please be quiet?Would you like coffee?⑤would 表示过去反复发生的动作。如：When I passed my school I would see my teachers who taught me 5 years ago.（3）needneed 作“必要”讲，既可作情态动词，也可作实义动词。作实义动词时后面的动词不定式要带to，其变化与一般动词相同。如：I need to think it over.---Need you go now? ---Yes, I must./No, I needn’t （4）daredare表示“敢”的意思。作为情态动词时，主要用在疑问句和否定句中。dare若作实义动词，后面可带to的不定式，此时to也可以省略。dare与need的用法相似。如：How dare you say that?She doesn’t date(to)ask her father.（5）used toused to表示过去常常发生的动作或存在的习惯，但现在已不复存在了。如：He used to smoke.（6）shall①shall作为情态动词用于第二、三人称，表示说话人的意愿，有“命令”、“警告、威胁、强制”和“允许”等意思。如：We shall do as our teacher says.You shall have the book as soon as I finish it.②在疑问句中，shall用于征求对方的意见或请求指示，常用于第一、第三人称。如：Where shall he wait for us?Shall we go out for a walk?Health is the most important thing in the world. Nothing is more important than health. If we take away our money, houses, or even our clothes, we can still survive. 36That is why we always try to eat in a healthy way and exercise regularly. How can we keep healthy? In order to eat healthily, I usually avoid eating food high in fat, like French fries or cookies, which are junk food. 37 I eat a lot of vegetables and fresh fruit which are full of vitamins. 38 Taking exercise every day helps us build a strong body. Regular exercise is an important part of keeping me healthy. What’s more, I think friends are an important part of one’s health. 39I always feel better when I am with friends than I am alone. When I am with friends, I always laugh.Laughing is also an important part of health. It's good to stay with my friends. By eating properly and exercising regularly, I can keep my mind as well as my body happy. These things sound easy to do, but not many people can manage them. 40A．On the other hand, doing exercise is very important. B．There are some people who like staying alone, but they keep healthy. C．Many students show that people with a wide range of social contacts don’t get sick. D．But if our health was taken away, it is certain that we would surely die. E．I think a strong will is necessary if we want to keep healthy.
