肯定句变否定句的规则肯定句改否定句的方法先观察句中是否有BE动词和情态动词，1、 如果有be动词，在be动词后加not即可。如：is not ， are not ， am not， was not， were not；2、 如果有情态动词，在can，should， will等后加not。如：cannot， should not， will not；3、 如果上述都没有的，在动词前加助动词否定形式dont/ doesnt/ didnt。注意：肯定句改成否定句时，some 改成any。练习把下面的句子变成否定句。1. She is watching TV now.2. We go to school on Sunday.3. His father works hard.4. Jacks mother is a nurse.5. The cat runs fast.6. They like reading books.7. My grandpa gives me a hot dog.8. Tom often walks to school.9. I have a doll.10. It is eating fish.