关系操作语言是高度非过程化的，因而使关系操作具备集合操作的特点，也就是______的

阅读理解。

     Do you believe there are aliens (外星人) ? Well, make a phone call and you will

know. A group of Americans can help. They make a device "talk" to aliens. If you

want to talk to an alien, you only need to visit www. Talk To Aliens . com , call l--900-2660300 and say, "Hello aliens. this is Earth calling. Can you hear me?" You can

say anything you want.

     But now. they only take phone calls from  people in the US. The call is $ 3. 99

every minute. After the hotline began in February, www. Talk To Aliens. com. has got hundreds of calls. There is one call every three minutes. They are also trying to send

people's e-mails. photos or videos into space.          

1. If you live in America and you want to know whether there are any aliens,         .

A. you can make a phone call

B. you can go to America for help

C. you can ask any scientist for help

D. you can talk to aliens

2. www. Talk To Aliens. com is a place where       .             

A. you can get some knowledge about aliens

B. you can talk to aliens

C. the aliens live

D. you can make a set of device to talk to aliens      

3. What does the underlined word refer to?      

A. The aliens.

B. The people who want to talk to aliens.

C. The Americans.

D. The group of scientists who can help you.                  

4. Which of the following is NOT right?

A. Only American people can call l-900-226-0300.

B. People from any country can call l-900-366-0300 now.

C. If you call the hotline for two minutes, you should pay $ 7. 98.

D. Every three minutes there someone is calling 1-900-226-0300.

5. From this article we know         .

A. there is only one call after the' hotline began in February

B. there are some aliens in the world

C. some Americans are trying to send information about humans into space

D. if you pay $2.99 for a minute, you can talk to aliens

关于絮凝有关说法中正确的是

A．发生絮凝条件是乳滴的电荷减少时，使电位降低，乳滴产生凝聚而成絮凝

B．絮凝与乳剂的黏度有关

C．絮凝与乳剂的相溶体积有关

D．乳剂中电解质和离子型乳化剂的存在是产生絮凝的主要原因

E．以上都不对

移动台在空闲状态下的小区选择和重选是由（）网络实体来决定的

下列关于幻灯片中文本的说法，错误的是（）。

A.在幻灯片中创建文本有多种方法，如文本占位符、文本框等

B.给文本设置字体、字号、字型称为文本的格式化

C.艺术字的编辑和普通文本的完全一样

D.文本可以动画显示

电抗器的选择步骤？