用户电缆线路传输损耗限值应不大于（）dB，少数边远地区的用户电缆线路其传输损耗可超过

根据课文原文，填入所缺内容。

★ It was not immediately obvious that water was     1   the development of life.

★ This produced ____2____, which made it possible for life to develop.

★ I earned my passage by working as an unpaid hand, which ____3_____.

★ When they crossed the Rocky mountain, they     4   some mountain goats and even a grizzly and an eagle.

★ Many of them _____5_____riding wild horses and can win thousands of dollars.

交际用语配对，从B栏中找出与A栏相对应的答语。（10分）

A                                                               B

1. Can you spell it?                                     

A．Thank you.

2. Are the basketballs next to the box?

B．All right.

3. Do you have a watch?

C．Yes, they are.

4. Your jacket is nice.

D．Yes. R-U-L-E-R, ruler.5. Please call John at 8964318.                  E. No, but I have a clock.

面向比特的同步控制(HDLC)协议的各种类型帧中，用于提供链路的建立、拆除及其他多种控制功能的帧为 (19) 。

A．信息帧

B．监视帧

C．无编号帧

D．控制帧

阻断乙酰胆碱M样作用的药物是

A．琥珀酰胆碱

B．毛果芸香碱

C．硫酸阿托品

D．烟碱

E．毒扁豆碱

目前，比较流行的UNIX系统属于哪一类操作系统

A．网络操作系统

B．分时操作系统

C．批处理操作系统

D．实时操作系统