问题 单项选择题

下列对分布式操作系统和网络网络操作系统的比较不正确的是( )。

A.分布式OS的网络控制功能是分布式的,而网络OS是集中式的

B.分布式OS的任务可分配到多个处理单元上并行执行,而网络OS通常在本地处理

C.分布式系统中各个站点的资源可供系统中所有用户共享,而网络OS通常仅由本机用户独占

D.分布式OS在可靠性方面较网络OS差,因此在应用上网络OS更普遍

答案

参考答案:D

解析:[分析] 由于分布式系统的处理和控制功能是分布的,因此任何结点上的故障,都不会给系统造成太大的影响,而网络操作系统,其控制功能大多集中在主机或服务器中,这使得系统具有潜在的不可靠性。

判断题
阅读理解

Searching the Internet may help middle-aged and older adults keep their memories sharp,US researchers said.

Researchers at the University of California, Los Angeles ,studied people doing web searches by recording their brain activity.

“What we saw was people who had Internet experience used more of their brain during the search,”Dr.Gary Small, a UCLA expert on aging, said,“This suggests that just searching on the Internet may train the brain and that it may keep it active and healthy.”

“This is the first time anyone has simulated(模拟)an Internet search task while scanning the brain,”Small said. His team studied 24 normal volunteers between the ages of 55 and 76. Half were experienced at searching the Internet and the other half had no web experience. However, the two groups were similar in age, gender and education.

Both groups were asked to do Internet searches and book reading tasks while their brain activity was monitored.

“We found that in the book reading task, the visual cortex— the part of the brain that controls reading and language — was activated,”Small said,“In doing the Internet search task, there was much greater activity, but only in the Internet-savvy(了解)group.”

He said it appears that people who are familiar with the Internet can engage in much deeper level of brain activity. Activities that keep the brain engaged can preserve brain health and thinking ability. Small thinks learning to do Internet searches may be one of those activities.

小题1:Researchers          when volunteers were doing web searches.

A.studied the Internet

B.activated the brain

C.recorded their memories

D.monitored the brain activity小题2:The two volunteer groups were         .

A.similar in education

B.of the same age

C.good at the computer

D.book lovers小题3:According to the passage, we can learn that         .

A.reading books keeps the brain more engaged

B.searching the web keeps the brain more engaged

C.watching TV keeps the brain more engaged

D.chatting online keeps the brain more engaged小题4:Which of the following is TRUE?

A.When you read, the whole brain will be activated.

B.Dr.Gary Small is a UCLA expert on brain health.

C.Internet searches can preserve brain health and thinking ability

D.People who read books may have a better memory.