[语法初识]
原句感知 ①But now his restaurant ought to be full of people. (1)以上句子中，句①④⑤⑥中的黑体②Does your father need any help? 词都是情态动词，而句②③中的黑体词③What do we need to take for the 是实义动词。 picnic? (2)以上各句中的情态动词后都接动词④There is enough time. You needn't 原形。其中句⑥中hurry. must_have_happened的意思是“一定⑤His mother is ill. He has to stay at 已经发生了”。 home to look after her. (3)上述句子中ought_to意为“应该”；⑥Something terrible must have need意为“需要”；has to意为“不得不”。 happened if Li Chang was not coming to eat in his restaurant as he always did.
[语法剖析]
自主探究 语法点一 ought to的用法 1．“应该”，表示责任或义务。用于表示按道理应当，常指客观的义务或责任，大多数情况下可用should代替，但比should语气重。
I'm his teacher. I ought to take care of him. 我是他的老师，我应该照顾他。
I should help her because she is in trouble. 她有困难了，我应该帮助她。
2．“应该”，表示劝告、建议或命令。should和ought to可通用，但在疑问句中常用should。ought to的否定式为oughtn't to或ought not to。
You ought to be more careful when you cross the road next time. 下次过马路时，你应该更小心些。 Should I open the window? 我可以打开窗户吗？
3．“应该”，表示推测。可与should换用。
It is already 9 o'clock; he ought to be in his office now. 已经9点了，现在他应该在他办公室了。 This is where the oil ought to/should be. 这里应该就是石油存在的地方。 即时演练1
用ought to完成句子
①他不应该缺席这么重要的会议。
He oughtn't/ought_not_to_be absent from such an important meeting. ②——我明天该动身吗？ ——是的，你应该。
—Ought_I_to_leave tomorrow? —Yes, you_ought_to． ③你应该比你哥哥学习更努力。
You ought_to_work_harder than your brother. 语法点二
1．作情态动词
(1)need作情态动词时，只能用于疑问句、否定句或条件句中，意为“需要”。 —Need I come tomorrow? —Yes, you must./ No, you needn't. ——我明天需要来吗？
——是的，你必须来。/不，没必要。
(2)needn't 意为“不必”，表示客观上不必如何。 We needn't hurry, for there's plenty of time. 我们不必这么匆忙，因为时间很充裕。 2．作实义动词
need作实义动词时，后可接名词、动名词、不定式等，有人称、时态和数的变化。
need的用法
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