问题 问答题 论述题

为什么强制存取控制提供了更高级别的数据库安全性?

答案

参考答案:

强制存取控制(MAC)是对数据本身进行密级标记,无论数据如何复制,标记与数据是一个不可分的整体,只有符合密级标记要求的用户才可以操纵数据,从而提供了更高级别的安全性。

阅读理解

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.

单项选择题