英语八年级【知识精讲】14.句法(9)肯定句和否定句课件

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这是一份英语八年级【知识精讲】14.句法(9)肯定句和否定句课件，共16页。

含有否定词nt,n,nthing,never等或表示部分否定的词hardly,seldm等的句子被称为否定句。不含否定词的句子就称为肯定句。Mr. Walker is an Englishman.He is nt an American.
肯定句变否定句的方法1.原句中含有be动词、助动词和情态动词时，在be动词、助动词或情态动词后直接加nt。 I am a teacher. → I am nt a teacher.  He will g t the z if it rains tmrrw.  →He wn't g t the z if it rains tmrrw.
2.原句中没有be动词，助动词或情态动词时，要在行为动词前加助动词与否定副词nt的缩写形式。 Mr Wang wrks in a factry.  →Mr Wang desn't wrk in a factry. Xia Lin visited ur friends last night.  →Xia Lin didn't visit ur friends last night.
肯定句变否定句的特殊情况1.祈使句变否定句时，一般在句首加Dn't，但Let us或Let's开头的祈使句在 Let us或 Let's后加nt即可。如：  Put them ver there．→Dn't put them ver there．Let us g hme．→Let us nt g hme．
2.主从复合句中，主句是I think，I believe等结构，变否定句时，形式上否定主句，实际上否定从句。如：  I dn't think chickens can swim ．我认为鸡不会游泳
3.肯定句中含有every-, sme- 的合成词，变否定句时常改为含有 n- 的合成词。Everything is ready. → Nthing is ready.  There is smething wrng with my bike.  → There is nthing wrng with my bike.
4.肯定句含有bth, , all时，变否定句时应改为neither, , nne如：Bth f us are students．→Neither f us is a student．All f them like bananas. → Nne f them like(s) bananas.
5.肯定句中含有always, usually和ever时，变否定句时改为never。如：   Lily always ges t the park n Sundays.→Lily never ges t the park n Sundays.
6.动词不定式变否定式时，常在不定式符号 t 前加 nt 。The teacher tells me t d it．→The teacher tells me nt t d it．My mther wants me t wash the dishes.→My mther wants me nt t wash the dishes.
按要求完成下列各题, 每空一词。I think he has smething t d. (改为否定句)I ________ ________ he has ________ t d.
答案：dn't think; anything
句型大变脸Yu'd better knw abut western table manners. (改为否定句)Yu ________ ________ ________ knw abut western table manners.
答案：had better nt