按要求改写句子。
1. This is my ruler. （改写为一般疑问句并作出肯定的回答）
2. Her dresser is near her bed.(变为否定句)
3. My keys are on the sofa. (对画线部分提问)
4. He is my good friend. (改为复数句)
Frank will fall behind in studies he works hard from now on．（ ）
A．unlessB．becauseC．if
Could you tell me by Wechat？（ ）
A．what can we doB．what we can do
C．what do we do
David， make trouble at school． （ ）
A．can'tB．don'tC．doesn't
Tony， come on， we'll miss the World Cup．（ ）
A．soB．andC．or
Must we finish the homework now？
Our teacher doesn't ask us to． （ ）
A．Yes， we mustB．No， we mustn't
C．No， we needn't