12Unit 3 Language in use祈使句结构如下： (Please) + do sth. (Please) + Don’t do sth.肯定：否定：DO ，可以放在动词前，为加强语气用。如： Do come in, please! Do listen to me, please! Do open the door, please!一、我们已经学习的表推测的情态动词有： must/can/could/may/might二、表推测的三种句式：1. 在肯定句中一般用 must ， can/could ， may/might ，程度逐渐减弱。 e.g. He must/may/might know the answer to this question. e.g. You have worked all this week. You must be tired.2. 在否定句中用 can’t/couldn’t ( 不可能 ) ， may not/ might not( 可能不 ) 。 e.g. It can’t /couldn’t be the headmaster. He has gone to America.e.g. He may not/might not know the scientist.3. 在疑问句中，一般只使用 can/could 。e.g. Could he have finished the task?e.g. Can he be at home now?Language practice That could be harmful!Betty, you must know!Stay away from windows and heavy furniture.Do not stand near street lights or under power lines.1. It is dangerous. You ________keep out!2. These stairs are not safe. You _______use them.3. The rocks are falling down. You ______get hit.4. The river is too deep. You ________swim in it.5. Betty _______know what to do , because she did some basic medical training.1 Complete the sentences with could, must or mustn’t.mustmustn'tcouldmustn'tmust 2 Underline the correct words to complete the first aid instructions. 1 Get / Do not get medical help immediately. 2 Ask / Do not ask them where the pain is. 3 Lift / Do not lift them because you may drop them. 4 Keep / Do not keep them warm.3 Complete the poster about earthquake with the correct form of the words and expressions in the box.do not use hide under keep leave stay away1 ____________from the windows.2 ___________a table.3 ___________the lift.4 ___...
