为你解答-变否定句.
1.Can you speak English well?
改：Can't you speak English well?
2.Do you have an appointment?
改：Don't you have an appointment?
3.Please clean the window.
改：Please don't clean the window.
4.You must smile to her warmly.
改：You needn't smile to her warmly.（说明：must的否定应改成needn't,不必的意思.）
5.He bought some pictuers yesterday.
改：He didn't buy any pictures yesterday.