问题 单项选择题

下面关于并行数据库的体系结构的叙述,比较全面的是 Ⅰ.共享内存结构 Ⅱ.共享磁盘结构 Ⅲ.无共享资源结构

A.Ⅰ和Ⅱ

B.Ⅱ和Ⅲ

C.Ⅰ和Ⅲ

D.Ⅰ,Ⅱ和Ⅲ

答案

参考答案:D

解析: 数据库的并行处理是提高数据库系统对事务快速响应能力的有效手段。并行数据库系统的体系结构主要有3种:共享内存结构;共享磁盘结构;无共享资源结构。并行数据库技术包括了对数据库的分区管理和并行查询。一个理想的并行数据库系统应能充分利用硬件平台的并行性,采用多进程、多线程的数据库结构,提供不同程度的并行性、不同用户事务间的并行性、同一事务内不同查询间的并行性、同一查询内不同操作间的并行性和同一操作内的并行性。

单项选择题 A型题
阅读理解

阅读理解。

     Can you believe your eyes? A recent experiment suggests that the answer to that question may depend

on your age.

     Martin Doherty, a psychologist at the University of Stirling in Scotland, led the team of scientists. In this

experiment, Doherty and his team tested the perception (观察力) of some people, using pictures of some

orange circles. The researchers showed the same pictures to two groups of people. The first group included

151 children aged 4 to 10, and the second group included 24 adults aged 18 to 25.

     The first group of pictures showed two circles alone on a white background. One of the circles was larger

than the other, and these people were asked to identify the larger one. Four-year-olds identified the correct

circle 79 percent of the time. Adults identified the correct circle 95 percent of the time.

     Next, both groups were shown a picture where the orange circles, again of different sizes, were surrounded

by gray circles. Here's where the trick lies in. In some of the pictures, the smaller orange circle was surrounded

by even smaller gray circles-making the orange circle appear larger than the other orange circle, which was

the real larger one. And the larger orange circle was surrounded by even bigger gray circles-so it appeared to

be smaller than the real smaller orange circle.

     When young children aged 4 to 6 looked at these tricky pictures, they weren't fooled-they were still able

to find the bigger circle with roughly the same accuracy as before. Older children and adults, on the other

hand, did not do as well. Older children often identified the smaller circle as the larger one, and adults got it

wrong most of the time.

     As children get older, Doherty said, their brains may develop the ability to identify visual context. In other

words, they will begin to process the whole picture at once: the tricky gray circles, as well as the orange

circle in the middle. As a result, they're more likely to fall for this kind of visual trick.

1. Doherty and his team of scientists did an experiment to evaluate _____. [ ]

A. children's and adults' eye-sight

B. people's ability to see accurately

C. children's and adults' brains

D. the influence of people's age

2. When asked to find the larger circle, _____. [ ]

A. children at 6 got it wrong 79% of the time with no gray ones around

B. only adults over 18 got it right 95% 0f the time with gray ones around

C. children at 4 got it right about 79% of the time with gray ones around

D. adults got it right most of the time with gray ones around

3. According to the passage, we can know that _____. [ ]

A. a smaller orange circle appears bigger on a white background

B. an orange circle appears bigger than a gray one of the same size

C. a circle surrounded by other circles looks bigger than its real size

D. a circle surrounded by bigger ones looks smaller than its real size

4. Visual context may work when children get older than _____. [ ]

A. 4

B. 6

C. 10

D. 18

5. Why are younger children not fooled? [ ]

A. Because they are smarter than older children and adults.

B. Because older people are influenced by their experience.

C. Because people's eyes become weaker as they grow older.

D. Because their brain can hardly notice related things together.