问题 单项选择题

下列安全协议中,用来实现安全电子邮件的协议是______。

A.IPSec
B.L2TP
C.PGP
D.PPTP

答案

参考答案:C

解析:PGP(Pretty Good Priracy),是一个基于RSA公钥加密体系的邮件加密软件。可以用它对邮件保密以防止非授权者阅读,它还能对邮件加上数字签名从而使收信人可以确认邮件的发送者,并能确信邮件不被篡改。它可以提供一种安全的通信方式,而事先并不需要任何保密的渠道用来传递密匙。它采用了一种RSA和传统加密的杂合算法,用于数字签名的邮件文摘算法、加密前压缩等,还有一个良好的人机工程设计。它的功能强大,有很快的速度。

阅读理解

根据短文内容,回答下列问题。

     Most new babies were born in the developing countries. These countries are found in Africa, South America

and parts of Asia. In the developed countries of Europe and North America, the population is growing very

slowly. This is because women in these countries have, on average (平均), only one or two children. In the

developing countries, many women have five or more children. In 1950, about one quarter of the world's

population lived in the developed countries. By 2050, these countries will be home to only about one tenth of the

world's people.

     In the developing countries, more than one billion people are still living below the poverty (贫困) line. These

people do not have enough food to eat and they live in poor housing conditions. Children get little time at school

and suffer (遭受痛苦) from many kinds of diseases.

     At the beginning of the 21st century, the world's population was around six billion. The U.N. has said that the

world's population will level off (平稳下降) at 12.5 billion by the year 2100. Other groups think the world's

population will continue to grow, reaching 14 billion before it becomes stable (稳定的), or even falls. 

1. In what areas of the world can developing countries be found?

   ________________________________________________

2. In 1950, what percent of the world's population lived in developing countries?

   ________________________________________________

3. How to describe the people who are living below the poverty line?

   ________________________________________________

4. There will be twelve and a half billion people on the earth in 2100, won't there?

   ________________________________________________

5. 将文中画线部分翻译成汉语。

   ________________________________________________

填空题