如果多项式4a⁴-（b-c）²=M（2a²-b+c），则M表示的多项式是（　　）

A．2a²-b+c

B．2a²-b-c

C．2a²+b-c

D．2a²+b+c

I''m surprised that he ____ to help me when I needed his help .

A．should refuse

B．would have refused

C．should have refused

D．may have refused