问题 单项选择题

富营养化后期的水体中()。

A.水草生长旺盛

B.微量元素减少

C.溶解氧含量明显减少

D.营养元素含量减少

E.硝酸盐含量过高

答案

参考答案:C

解析:

藻类等浮游生物大量繁殖形成水体富营养化,藻类繁殖迅速,生长周期短,死亡后通过细菌分解,不断消耗水中的溶解氧使水质恶化。因此,选项C正确。

阅读理解

阅读理解。

     Every year thousands of people get hurt or die when they are crossing the road. Most of these people are

old people and children. Old people often get hurt or die because they can't see or hear very well. Children

usually meet with accidents because of their carelessness. They forget to look and listen before they cross the

road.

     How can we lessen (减少) traffic accidents? All of us must obey the traffic rules. For the drivers, they

shouldn't drive too fast. If they drive too fast, it will be very difficult to stop the cars in a very short time. For

the pedestrians (行人), it's very important to be careful when they are walking on the road. Therefore, when

we walk across the road, we must try to walk along the pavements. We must stop and look both ways before

crossing the road. Look left first, next look right, and then look left again. Only when we are sure that the road

is clear can we cross it. The right way to cross the road is to walk quickly. It's not safe to run. If people run

across the road, they may fall down. Teens should try to help children, old people or blind people to cross the

road, and never play in the street.

1. Which of the following is NOT the right way to cross the road?

A. Stop and look both ways.

B. Run quickly.

C. Make sure that the road is clear.

D. Walk quickly.

2. Why do most old people often get hurt or die when they are crossing the road?

A. Because they are not careful.

B. Because they forget to look and listen.

C. Because they can't see or hear very well.

D. Because they often run across the road.

3. As a student, you can _____ to try to lessen traffic accidents.

A. help children to cross the road

B. play in the street carefully

C. run across the road quickly

D. let drivers drive slowly

单项选择题