“ ______ I hand in the paper this week?” “ No, you ______. You _____ hand it in next week.

A．Must; needn’t; may

B．will; mustn’t; ought to

C．Shall; can’t; have to

D．Should; didn’t have to; can

为什么摩擦性失业是不可避免的？政府如何降低摩擦性失业的数量？