NPT5型空气压缩机气阀开度为（）mm。A、1.5—20 B、0.15—0.20 C

—Got your driving license?

—No. I ________ too busy to have enough practice, so I didn't take the driving test last week.[ ]

A. will be  

B. am

C. have been  

D. had been

(73) is the sending and receiving of the message by computer. It is a fast, low-cost way of communicating worldwide。

A．WWW

B．E-mail

C．TFTP

D．TELNET

氦气对健康的危害有哪些？

读图，回答下列问题。

位于山顶甲的（）方向，D、G两地的相对高度是（）。