有人欲配制下列含有四种不同阴、阳离子的溶液，其中能配制成功的是（ ） A．Ca2

阅读理解。

     You know that the sea is salty. You can taste the salt. Some parts of the sea are saltier than other

parts. There is one sea, called the Dead Sea, which is very salty. It is so salty that swimmers cannot

sink! Fish cannot live in the Dead Sea. What a strange sea!

     The sea can be very cold. Divers, who dive deep down in the sea know this. On the top the water

may be warm. When the diver goes downwards, the sea becomes colder and colder. Another thing

happens. When the diver goes deeper, the water presses up on him. So the diver has to wear clothes

made of metal. Some people who want to go very deep use a very strong diving ship!

1. The water in the Dead Sea is _____ the water in other seas.

A. as salty as                    

B. not so salty as    

C. much saltier than              

D. more salty than

2. Fish cannot live _____ .

A. in the sea                    

B. in the river    

C. in the lake                  

D. in the Dead Sea

3. If you dive deep down into the sea, you will have to wear clothes _____.

A. made of metal                

B. made of iron  

C. made of cotton                

D. made of nylon

4. The water on the top of the sea is _____that at the bottom of it.

A. much warmer than              

B. much colder than    

C. as warm as                    

D. as cold as

5. Which of the following is TRUE?

A. Everyone can't swim in the sea.    

B. No one can swim in the river.

C. Each one can swim in the lake.      

D. Everyone can swim in the Dead Sea.

康明斯柴油机中型号PT（G）-AFC中的AFC的含义是（）。

A.电子调速

B.空燃比控制

C.机械调速

D.以上都不对

能健脾补中，化湿和胃的药物是( )。

A．白术
B．山药
C．白扁豆
D．黄芪
E．太子参

关于帕金森病的药物治疗原则，以下表述正确的是

A．早期发现，早期诊断，早期治疗

B．早期药物治疗能够阻止病情发展

C．坚持单一用药

D．小剂量开始，缓慢递增，不求全效

E．长期坚持规律用药可以阻止病情进展

简述文书、公文和文件的三者之间的区别与联系及三者的概念起源。