[语法初识]

原句感知 自主探究 ①But now his restaurant ought to be full of people.

②Does your father need any help?

③What do we need to take for the picnic?

④There is enough time. You needn't hurry.

⑤His mother is ill. He has to stay at home to look after her.

⑥Something terrible must have happened if Li Chang was not coming to eat in his restaurant as he always did. (1)以上句子中，句①④⑤⑥中的黑体词都是情态动词，而句②③中的黑体词是实义动词。

(2)以上各句中的情态动词后都接动词原形。其中句⑥中must_have_happened的意思是"一定已经发生了"。

(3)上述句子中ought_to意为"应该"；need意为"需要"；has to意为"不得不"。

　　[语法剖析]

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