因式分

（1）a²（x-y）-4b²（x-y）            

（2）a³+6a²+9a

（3）m²+2n-mn-2m                  

（4）x²-7x+10．

If you don't move, you may sit at ______ this end ______ that end of the boat. [ ]

A. between, and

B. either, or

C. both, and

D. neither, nor