问题 选择题

下列说法正确的是(       )

A.相对原子质量和相对分子质量分别是原子、分子的质量

B.铁生锈是缓慢氧化,属于物理变化

C.构成物质粒子有分子、原子、离子等

D.由同种元素组成的物质叫单质

答案

答案:C

题目分析:A、原子质量是原子的实际质量,单位为g或Kg,而相对原子质量只是一个比值,故A说法错误;

B、铁生锈是缓慢氧化,有新的物质生成,属于化学变化,故B说法错误;

C、物质构成的微粒有分子、原子、离子,故C说法正确;

D、由同种元素组成的纯净物叫做单质,氧气、臭氧都是氧元素组成的,但二者混合后只含一种元素氧元素,属于混合物,故D说法错误;

故选C。

点评:本题难度不大,对于基本概念的理解同学们要重点掌握概念中的关键词语。

阅读理解

     Life on earth depends on water, and there is no substitute for it. The current assumption is that our

basic needs for water-whether for drinking, agriculture, industry or the raising of fish will always have to

be met. Given that premise (前提) , there are two basic routes we can go:more equal access to water or

better engineering solutions.

     Looking at the engineering solution first, a lot of my research concentrates on what happens to

wetlands when you build dams in river basins, particularly in Africa. The ecology of such areas is almost

entirely driven by the seasonal changes of the river-the pulse of the water. And the fact is that if you build

a dam, you generally spoil the downstream ecology. In the past, such problems have been hidden by a

lack of information. But in the near future, governments will have no excuse for their ignorance.

    The engineers' ability to control water flows has created new kinds of unpredictability too. Dams in

Africa have meant fewer fish, less grazing and less flood- plain (洪泛区) agriculture-none of which were

expected. And their average economic life is assumed to be thirty years. Dams don't exist forever, but

what will replace them is not clear.

     The challenge for the future is to find new means of controlling water. Although GM technology

(转基因) will allow us to breed better dry land crops, there is no market for companies to develop

crops suitable for the micro-climates of the Sahel and elsewhere in Africa. Who is going to pay for

research on locally appropriate crops in the Third World?

1. What's the main idea of this passage?  

A. The challenge for the future.

B. The engineering solutions to water resource and their limitation.

C. The basic means of controlling water.

D. The challenge for developing crops.

2. Which of the following statements is NOT true for meeting our basic needs for water? 

A. Water resource should be used more reasonably.

B. More dams should be built in river basins.

C. More wetlands should be protected from destruction.

D. More dry-land crops could be developed in Africa.

3. The author suggests that governments will have no excuse for their careless ignorance in the future

because      

A. the ecological destruction will be known to the public by researchers

B. the ecological destruction will no longer be a problem in the future

C. the future is an information age

D. governments will face greater challenge in the future

4. The author mentions all the problems caused by dams EXCEPT      

A. fewer fish

B. less grazing land

C. less farming land

D. less floodplain agriculture

5. The last sentence probably implies that           .   

A. no one will invest in developing locally appropriate crops in Africa

B. researchers have no interest in developing dry land crops

C. research on locally appropriate crops in the Third World may be profitable

D. There is less water resource in the Third World

单项选择题