电路图上部的4根导线分别标以“30”“15”“X”“31”，其中“X”表示（）。A、

在质量数据特征值中，可以用来描述离散趋势的特征值是( )。

A．总体平均值

B．样本平均值

C．中位数

D．变异系数

用括号中词语的正确形式填空。

1. It is ______ (polite) to leave without saying goodbye to the host.

2. These containers can be used again.  So they are called ______ (use) containers.

3. The doctor said the old man's condition was ______ (hope) because the operation was not successful.

4. Those small factories are causing a lot of ______ (environment) ______ (pollute) with all their noise

    and smoke.

5. The more exercise young students take, the more ______ (energy) they will become.

6. The ______ (nation) emblem (国徽)of England is a rose.

7. The lecture was ______ (agree) to Tom, so he fell asleep quickly.

8. Human beings are ______ (create) animals.  They have created a lot of wonders.

主变压器的接线为Y，dll，当装设纵差保护时，电流互感器的接线应为()。

A．Y,y

B．D,d

C．D,y

D．Y,d

市场细分有什么作用？

检测工作中，班组成员严格按照仪器设备操作规范、标准作业卡进行现场检测，检测现场应无杂物，使用的工器具、材料应摆放整齐有序及时排除（）以及环境干扰问题。

A.检测方法、检测仪器

B.检测标准、检测方法

C.检测手段、检测仪器

D.检测手段、检测标准