—Can you tell me ________ to send this postcard to New York by airmail?

—Let me check. Oh，it’s one dollar.

A．how long it takes

B．how much it costs

C．who can help me

D．if there’s a post office

计算机病毒是侵入计算机系统并具有潜伏、传播和破坏能力的( )。

A．生物

B．程序

C．指令

D．细菌