【正文】 be at home. 注意： might 表示推測時，不表示時態(tài)。 You mustn39。 If Tom didn39。 Your mother must have been looking for you. 你媽媽一定一直在找你。 Ought he to go? Yes. I think he ought to. 表示要求，命令時，語氣由 should（應(yīng)該）、 had better 最好）、 must（必須）漸強(qiáng)。t have to. 典型例題 1） Could I borrow your dictionary? Yes, of course, you____. A. might B. will C. can D. should 答案 C. could 表示委婉的語氣，并不為時態(tài)。 shouldn39。 比較 need 和 dare 這兩詞既可做實(shí)義動詞用，又可做情態(tài)動詞用。t use to play tennis before she was fourteen. You ought not to have told her all about it. Ought he to see a heart specialist at once.? ought to 本身作為情態(tài)動詞使用。 wouldn39。t you 是一種委婉語氣。） ought to 在語氣上比 should 要強(qiáng)。 We would have finished this work by the end of next December. 明年十二月底前我們很可能已完成這項(xiàng)工作了。 Why didn39。 He had to look after his sister yesterday. 3） 在否定結(jié)構(gòu)中： don39。t. 2）在否定，疑問句中表示推測或懷疑。例如： When the crops fail, the people go hungry. I always go red when I’m embarrassed. We’d better eat these apples before they go bad. every time 在句中引導(dǎo)一個狀語從句，表示 “每次 ……, 每當(dāng) ……” 。例如： He lives on his own. I need some time on my own. 2. You must keep to the path. Keep to 的意思是 “沿著 …… 走； 使不離開； 留在某個位置 ”。 4） 情態(tài)動詞沒有非謂語形式，即沒有不定式，分詞，等形式。只 是可能性比 may 小。t tell him about it. 你一定不要把這件事告訴他。t leave here until five o39。 5）推測的否定形式，疑問形式用 can39。 had better表示 最好 had better 相當(dāng)于一個助動詞，它只有一種形式，它后面要跟動詞 原形。答語中 of course，表示肯定的語氣，允許某人做 某事時，用 can 和 may 來表達(dá)，不能用 could 或 might。t 不應(yīng)該。作為情態(tài)動詞，兩者都只能用于疑問句，否定句和條件句。它們的疑問，否定形式應(yīng)予以注意： Do they have to pay their bill before the end of the month? She didn39。t 不必，不用。 Would you like some cake? 3）否定結(jié)構(gòu)中用 will，一般不用 would, won39。 You ought to (should) have been more careful in this experiment. He ought not to have thrown the old clothes away.（事實(shí)上已扔了。 表示對過去情況的推測。 4) must 表示對過去某時正發(fā)生的事情的推測， must 后面要接不定式的完成進(jìn)行式。但 must 可用于間接引語中表示過去的必要或義務(wù)。 Could I have the television on