问题 填空题

在半径为4cm的圆中,挖去一个半径为x(cm)的圆面,剩下一个圆环的面积为y(cm2),则y与x的函数关系式为______,其中自变量x的取值范围是______.

答案

半径为4cm的圆的面积为16π,半径为x的圆的面积为:πx2,则函数解析式是:y=16π-πx2,且0<x<4.

阅读理解

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 a 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.

1. Researchers _____ when volunteers were doing web searches. 

A. studied the Internet

B. activated the brain

C. monitored the brain activity

D. recorded their memories

2. The two volunteer groups were _____.

A. of the same age

B. similar in education

C. good at the computer

D. book lovers

3. According to the passage, we can learn that _____.

A. searching the web keeps the brain more engaged

B. reading books keeps the brain more engaged

C. watching TV keeps the brain more engaged

D. chatting online keeps the brain more engaged

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. People who read books may have a better memory.

D. Internet searches can preserve brain health and thinking ability

5. What can we conclude from the last paragraph?

A. Web searching is good for the brain.

B. Web searching damages the brain.

C. Activities are good for the brain.

D. Activities damage the brain.

单项选择题