属于监测管理的传染病是（） A.艾滋病 B.梅毒 C.百日咳 D.流行性

He told me that he wanted to buy his daughter a new bag as her old onehas been stolen.

A                         B        C    D

下列虚基类的声明中，正确的是( )。

A．class virtual B: public A

B．virtual class B: public A

C．class B: public A virtual

D．class B: virtual public A

生产中使用最广泛的冷却剂是空气。