主系表结构疑问句把be动词提前否定句be后面加not主谓结构疑问句句首加do动词恢复原形否定句在动词前加don't或doesn't动词恢复原形1.在be动词后加not。
如:is not , are not , am not2.在can,should, will等后加not。如:can not, should not,will not;3.上述都没有的,在动词前加助动词否定形式don't/doesn't/didn't。
4. some 改成any。如:I am a girl. → I am not a girl.You are a student. →You are not a student.→You aren't a student.This is Tom's bag, → This is not Tom's bag.→ This isn't Tom's bag.