我会根据图片和首字母将句子补充完整。

1. What's this in E____________?  It's a s____________. 

2. What can you do?  I can m____________ the bed. 

3. What does Mike often do at home?  He often d____________ the dishes. 

4. How o____________ are you?  I'm f____________. 

5. I have a l____________ n____________. 

如果M=3x²-2xy-4y²，N=4x²+5xy-y²，则8x²-13xy-15y²等于（　　）

A．2M-3N

B．2M-N

C．3M-2N

D．4M-N