问题 单项选择题 A1/A2型题

正常人心率超过180次/分时,引起心输出量减少的主要原因是()。

A.心室充盈时间明显缩短,充盈量减少

B.心室舒张期过长,心室充盈早已接近限度

C.快速射血期缩短

D.慢速射血期缩短

E.迷走神经活动加强

答案

参考答案:A

解析:心率增快,心输出量增加,但有一定限度。如果心率过快,超过170~180次/分,心室充盈时间明显缩短,充盈量减少,搏出量可减少一半左右,心输出量亦开始下降。

阅读理解

阅读理解。

     Television has a huge influence on our lives. It is one of the most important ways of getting information.

People spend part of their spare time watching television, and much of what they learn comes from it.

     What we see on TV - movies,news shows, sports shows, advertisements and so on have increased our

knowledge and have changed the way we learn about the world today. However, not everything on TV is true.

     Most of the viewers (观众) are children. Television sometimes is like a baby-sitter. It spends more time

with children than parents do. But it keeps them in the living room away from healthy outdoor activities. They

spend less time playing soccer or walking in the park or playing games in the yard.

     Of course, there are some programs on TV that are good for children. But there are also some shows

which are bad. Children should not watch unhealthy shows. Maybe we can't change what is on TV, but we

can choose what we watch. Do you agree?

1. According to the passage, ________ is one of the most important ways of getting information.

A. a book

B. a computer

C. TV

2. ________ can't be got on Television.

A. Knowledge

B. Sports news

C. Computer games

3. The underlined word "baby-sitter" means ________.

A. 小妹妹

B. 保育员

C. 女婴

4. What can we do with programs on TV?

A. We can surely change them.

B. We can do nothing.

C. We can choose them.

5. From the passage, we may know ________.

A. TV is both good and bad for children.

B. Everything is true on TV.

C. All programs on TV are suitable for children.

单项选择题