1. I'm writing a letter.（变为一般疑问句）
        you        a letter?
2. They are playing soccer at school.（对划线部分提问）
                 they playing soccer?
3. Mr Green is playing the guitar.(对划线部分提问）
         Mr. Green         ?
4. They're talking to an old man.（对划线部分提问）
                 they talking to?
5. He often plays football in the afternoon.（用now替换often改写句子）
He                 football now.