Anderson is one of those（）appear friendly but in fact are hard to deal with.

A. who

B. they

C. that

D. which

一个多项式减去x²-2y²等于x²+y²，则这个多项式是（　　）

A．-2x²+y²

B．2x²-y²

C．x²-2y²

D．-x²+2y²