—How much are these green bags?

—_____ 50 dollars. [ ]

A. Yes. They are      

B. they are

C. They are            

D. It is

麻醉前用药的基本原则错误的是（）。

A．年老体弱休克甲低镇静药减量

B．产妇慎用或禁用中枢性镇痛药

C．小儿抗胆碱药按体重计算剂量比成人小

D．复合用药时应酌减剂量