一"Peter, have you got your new flat furnished?

—Yes. I ______ some used furniture and it was a real bargain.

A．will buy

B．have bought

C．bought

D．had bought

因式分

（1）2x³-4x²y³+6x²y²；

（2）3a²-27；

（3）（x+2y-z）²-（x-2y+z）²；

（4）-4a²x²+8ax-4．