九年级英语上学期Unit5学案

九年级英语上学期Unit5学案,标签：中学英语教案,http://www.xuehuiba.com
    eg. We should/ought to go and see our teacher tomorrow.(两者都可以)
    We ought to go, but I don't think we will because we have much work to do.(只能用ought to)
    ⑵must/have to表示"必须",在语气上比"应该"更强烈。
    ① must表示现在"必须";用will/shall have to 表示将来的"必须",用had to的形式表示过去的"必须"。
    eg. They must finish their work first.(表现在)
    They will have to finish their work first. (表将来)
    They had to finish their work first. (表过去)
    ② must/have to表示"必须"时意义相近, 但在用法上略有区别:must侧重于表示说话人的主观意志;have to侧重于表示客观需要。
    eg. It's raining hard. I have to go.(指外界客观环境要求)
    I'm tired. I must go home.(自己主观上的要求)
    ③ have to 的否定形式为don't have to = needn't, 表示不必要;
    must 的否定形式为mustn't表示禁止;不允许;一定不要。
    ⑶had better表示"最好",用于表示对别人的劝告、建议或表示一种愿望。缩写形式为 'd better。had better后面加动词原形,否定形式为had better not do sth.表示"最好不做……"。
    eg. You look tired. You'd better see a doctor.
    C、"why not", "why don't you" 和 "perhaps" 表示建议时的用法。
    ⑴"why not" 句型常用于说话人向对方提出一个建议, 意思是"何不……?"它和"why don't you"句型为同义句,后面都要加动词原形,即why not do sth? 和Why don't you do sth.?
    eg. Why don't you go to the cinema with your mother?
    = Why not go to the cinema with your mother?
    ⑵"perhaps"表示"可能",一般放在句首向对方提一个建议。
    eg. A:I want to be as strong as Tom.
    B: Perhaps you should exercise more.

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