如果句子里面有了be动词am is are,改否定句的时候直接在后面加上not就好了,而如果句中没有be动词,就要用助动词。例如:I have a book.就要改成:I do not have a book ?,当人称是三单:he,she,it或者一个物体,一个人的时候,助动词用dose ,但是dose用在否定句中,后面的动词要改为原型,如:He has a book.否定句:He dose not have a book.所以在句中没有be动词时,直接在主语后,动词前加上助动词和not就可以了。
有BE动词的句子用BE 加NOT ,例如,he is not a teacher./they weren't our classmates.如果句子是有实义动词的句子,那就是用助动词啦,比如,kate doesn't want to go to school./you didn't finish your mother's task. 总之呢,就是看你原来肯定句中是否有BE动词啦。听懂了没?你读初中吧?本回答被网友采纳