The word "breakthrough" is often used wh

NO．7信令不具有以下特点中的（）特点.

A.速度快

B.容量大

C.成本高

D.统一信令系统

以下IP地址中，不属于专用IP地址的是______。

A．10．1．8．1

B．172．12．8．1

C．172．30．8．1

D．192．168．8．1

ST型缓冲器组装螺母前，推力锥上平面与箱体顶部距离不得小于（）。

In the following essay, each blank has four choices. Choose the best answer and write down on the answer sheet.

Microwave communication uses (1) -frequency radio waves that travel in straightline sthrough the air. Because the waves cannot (2) with the curvature of the earth, they can be (3) only over short distance. Thus, microwave is a good (4) for sending data between buildings in a city or on a large college campus. For longer distances, the waves must be relayed by means of" dishes" or (5) . These can be installed on towers, highbuildings, and mountain tops.

4（）

A．material

B．equipment

C．medium

D．channel

季节性劳动保护工作都有哪些内容？