—Excuse me, Mum. When can we have dinner?

—Not until it   in half an hour.

A．is prepared

B．has been prepared

C．will be prepared

D．was prepared

哪一种药物最常应用于治疗冠心病变异型心绞痛发作（）

A.硝酸酯类

B.β受体阻断剂

C.洋地黄类

D.钙离子通道阻断剂

E.胺碘酮