1、Unit 4 Dont eat in class.,祈使句 1.定义。 用来表达命令、请求、劝告、警告、禁止等的句子叫作祈使句。祈使句通常省略主语you。例如: Be quiet,please.请安静。 Please have a seat.请坐。 2.句式结构。 ( 1 )Do型:动词原形+宾语+其他。例如: Go this way,please.请这边走。 ( 2 )Be型:Be+表语+其他。例如: Be a good kid!做个好孩子!,( 3 )Let型:Let+宾语+动词原形+其他。例如: Let me help you.让我来帮你。 注意:祈使句的否定形式一般是在动词原形前加do
2、nt构成,有时也可直接用no开头表示禁止。例如: Dont be late for school!上学不要迟到! No smoking!禁止吸烟!,have to与must的用法 have to和must均可表示“必须”。must更加强调说话者的主观意愿;而have to强调客观的必要性,意为“不得不”。两者的否定式含义大不相同。mustnt表示“不准;禁止”,而dont have to 表示“不必”。例如: I must go now,or Ill be late.我现在必须走了,不然我就会迟到了。 She has to help her mother look after her sist
3、er.她不得不帮着她妈妈照顾妹妹。 You mustnt swim in the river.你不准在河里游泳。 You dont have to do it now.你现在不必做这件事。 注意:以must开头的一般疑问句,其肯定回答用must,否定回答用neednt或dont have to。例如: Must I finish the work now?我现在必须完成这项工作吗? Yes,you must./No,you dont have to.是的,你必须完成。/不,你不必现在完成。,.根据句意用所给词的适当形式填空 1. Do ( do ) the work right now,Jim
4、 2.Please tell ( tell ) me the news. 3.Lets play ( play ) soccer now. 4.You must come ( come ) to school on time. 5.No talking ( talk ) here! .根据句意用must或have to的适当形式填空 1.You must do it yourself. 2. Must I read the book in the reading room? No,you dont have to . 3.Its late.Jim has to go home. 4. Mus
5、t Lily keep quiet? Yes,she must . 5.You dont have to get up early on weekends.,.按要求完成句子,每空一词 1.You cant listen to music when your mother is sleeping.( 改为祈使句 )Dont listen to music when your mother is sleeping. 2.He has to be in bed by ten oclock.( 改为一般疑问句 )Does he have to be in bed by ten oclock? 3.You must come here early this afternoon.( 改为祈使句 )Come here early this afternoon. 4.Let her help you.( 改为否定句 )Dont let her help you. 5.She has to ride her bike to go home.( 改为否定句 ) She doesnt have to ride her bike to go home.,
