问题 单项选择题

在公钥体制中,不公开的是______。 Ⅰ.公钥 Ⅱ.私钥 Ⅲ.加密算法

A.Ⅰ

B.Ⅱ

C.Ⅰ和Ⅱ

D.Ⅱ和Ⅲ

答案

参考答案:B

解析: 公钥密码体制有两个不同的密钥,它可将加密功能和解密功能分开。一个密钥为私钥,它被秘密保存。另一个密钥称为公钥,不需要保密,公钥加密算法和公钥都是公开的。

阅读理解

From the beginning rivers have played an important in the life of man.Man of the earliest times used the rivers as a means of travel.Today rivers still serve as a great waterway for the transport and people.

In ancient times, man settled near rivers or on river banks and built up large empires.

Water is nature’s most valuable gift to man.Man needs water to irrigate his crops, to cook and to wash.In nations all over the world, rivers mean life and wealth.They feed and clothe the nations around them.

Water is also a source of energy and power.Man build huge dams across the rivers to control the water for irrigation and get the energy needed to drive generators.The electrical power is then directed to homes, cities, factories and television stations.

Man uses water each day.In a small way rivers help to keep man in good health and provide for his amusements.Various forms of water sports keep man strong and healthy.

小题1:Rivers have been important to man _______.

A.since they came into being

B.since the last century

C.since a few hundred years ago.

D.since the beginning of BC小题2:Man in old times traveled from one continent to another ______.

A.by air

B.by sea

C.by train

D.by bus小题3:Generators are machines that are used ______.

A.to direct electrical power

B.to control the water

C.to produce electricit

D.to build dams y小题4:Which of the following statements is true?

A.People get energy by building bridges across rivers.

B.In ancient times large empires grew up near dams.

C.People can be provided with amusements in small rivers.

D.Large rivers are still useful for transportation in modern times.

单项选择题