爱华网肯定句变为否定句时应注意的特殊情况
肯定句变为否定句时，通常必须在句中加上副词not 。可是对有些特殊的情况我们还必须加以注意，现根据初中英语教材对这些特殊情况说明如下：
1.如果肯定句中有连词 and ，变为否定句时，通常要将 and 变为 or 。例如：
Thegirl can sing and dance. → The girl cannot sing ordance.
Theboy has father and mother. → The boy has no father ormother.
（或The boy has not any father or mother. ）
2.如果肯定句中 some ，变为否定句时， some 一般要改为 any 。例如：
Thereare some boys in the room. → There are not any boys in theroom.
3.如果肯定句中有 too （也），变为否定句时，应将 too 改为 either 。例如：
WangLing is a teacher, too. → Wang Ling is not a teacher,either.
4.如果肯定句中有 already ，变为否定句时，应将 already 改为 yet ，并放在句末。例如：
Theworker has finished his work already. → The worker has not finishedhis work yet.
5.如果肯定句中有“ had better ”，变为否定句时， not 要放在“ had better”之后。例如：
Youhad better write to your teacher. → You had better not write toyour teacher.
6.如果肯定句中有 always ，变为否定句时，要将 always 改为 never 。例如：
Shealways goes to school at seven o'clock. → She never goes to schoolat seven o'clock.
7.如果肯定句中有 both ，变为否定句时，要将 both 改为 neither 。例如：
Bothof us know English. → Neither of us knows English.
8.如果肯定句中有 all ，变为否定句时，要将 all 改为 none 。例如：
Allof these books are yours. → None of these books are ( is )yours.
9.如果肯定句中有 everybody ，变为否定句时，要将 everybody 改为 nobody 。例如：
Everybodyhas read the book. → Nobody has read the book.
10.如果肯定句中有 everything ，变为否定句时，要将 everything 改为 nothing 。例如：
Everythingis difficult for us. → Nothing is difficult for us.
11.如果肯定句中有情态动词 must ，变为否定句时，其变化要按 must 在句中的确切含意而定。如表示“不必”时，用“ need not( needn't ) ”；如表示“不准，不应是”时，则用“ must not ( mustn't )”。例如：
Youmust finish your work this afternoon. → You needn'd finish yourwork this afternoon.
Thecar must be parked here. → The car mustn't be parkedhere.
12.在谓语动词为 think, believe等后面接宾语从句时，习惯上将从句中的否定形式转移到主句的谓语部分中去。例如：
Ithink that my sister will be back soon. → I don't think that mysister will be back soon.
Ibelive that he will go to school tomorrow. → I don't belive that hewill go to school tomorrow.
