问题 名词解释

非对称加密

答案

参考答案:

在非对称加密体系中,密钥被分解为一对,即一把公开密钥和一把专用密钥。这对密钥中的任何一把都可作为公开密钥通过非保密方式向他人公开,而另一把则作为专用密钥加以保存。公开密钥用于对机密性的加密,专用密钥则用于对加密信息的解密。

单项选择题

The fact that most Americans live in urban areas does not mean that they reside in the center of large cities. In fact, more Americans live in the suburbs of large metropolitan areas than in the cities themselves.
The Bureau of the Census regards any area with more than 2,500 people as an urban area, and does not consider boundaries of cities and suburbs.
According to the Bureau, the political boundaries are less significant than the social and economic relationships and the transportation and communication systems that integrate a locale. The term used by the Bureau for an integrated metropolis is an MSA, which stands for Metropolitan Statistical Area. In general, an MSA is any area that contains a city and its surrounding suburbs and has a total population of 50,000 or more.
At the present time, the Bureau reports more than 280 MSAs, which together account for 75 percent of the U.S. population. In addition, the Bureau recognizes 18 megapolises, that is, continuous adjacent metropolitan areas. One of the most obvious megapolises includes a chain of hundreds of cities and suburbs across 10 states on the East Coast from Massachusetts to Virginia, including Boston, New York, and Washington D. C. In the Eastern Corridor, as it is called, a population of 45 million inhabitants is concentrated. Another megapolis that is growing rapidly is the California coast from San Francisco through Los Angeles to San Diego.

According to the passage, what is a megapolis

A.One of the 10 largest cities in the United States.

B.One of the 18 largest cities in the United States.

C.One of the 100 cities between Boston and Washington.

D.Any number of continuous adjacent cities and suburbs.

填空题