问题 单项选择题

在IPv4向IPv6过渡的方案中,当IPv6数据报进入IPv4网络时,将IPv6数据报封装成为IPv4数据报进行传输的方案是______。

A.双协议栈

B.多协议栈

C.协议路由器

D.隧道技术

答案

参考答案:D

解析:[分析] 从IPv4向IPv6过渡技术主要有3种:兼容IPv4的IPv6地址、双IP协议栈和基于IPv4隧道 技术的IPv6。

阅读理解

阅读理解

     Frederick Law Olmsted (1822-1903), a Connecticut farm boy, saw his first public park in

Liverpool, England, as he accompanied his brother on a walking tour. He was impressed by the park's

winding paths, open fields, lakes and bridges. Perhaps the most wonderful things of all was that the park

was open to everyone.

     A moment beginning in 1840 to set aside park land on New York City's Manhattan Island had a

successful result in 1856 with the purchase of 840 acres of rocky and swampy (沼泽的) land, bought

with about $5 million in state funds. Olmsted's chance of meeting with a project organizer led to his

applying for the job of the park manager. In 1857 Olmsted was appointed manager of the proposed

park, and the clearing of the site began.

     Calvert Vaux, a British architect, asked Olmsted to collaborate with him on a park design, and

Olmsted agreed. Vaux saw the park as a work of art, while Olmsted saw the park as a place for people

to escape the noise of the city. Together they invented a plan that would give the persons and animals

living in the city a quiet, green park and would also preserve and increase the good qualities of the natural

features of the land. The commissioners voted in favor of Vaux and Olmsted's plan, and in 1858, the two

became the official designers of New York City's Central Park.

     It took cartloads of topsoil to build Central Park's gentle slopes, shady glens, and steep, rocky

ravines.Five million trees were planted, a watersupply system was laid, and bridges, arches, roads and

paths were constructed. The park officially opened in 1876, and today, well over a century later, people

still escape the noise of the city in Olmsted and Vaux's great work of art.

1. What is the text mainly about?

A. A history of the planning of Central Park.

B. An engineering plan for Central Park.

C. A biography of Frederick Law Olmsted.

D. A guided walking tour of Central Park.

2. Olmsted became manager of Central Park because of________.

A. his friendship with Calvert Vaux

B. his hard work in clearing the land

C. his winning a design competition

D. a chance of meeting with one of the park's organizers

3. The underlined word "collaborate" in the third paragraph means "________".

A. disagree  

B. comment

C. vote  

D. work together

4. Which of the following is TRUE about Central Park?

A. It is out of date nowadays.

B. The designers came from the same country.

C. It is an old park in America.

D. It is only for people who can well afford it.

单项选择题