问题 选择题

下列各种自然现象形成的过程中,属于凝华的是(  )

A.春天,冰雪消融

B.夏天,冰箱门口飘出的“白气”

C.秋天,草丛之上晶莹的露珠

D.冬天,纷纷飘落的雪花

答案

A、冰雪融化,即物质由固态变为液态,即为熔化现象,故不符合题意;

B、夏天,冰箱门口会飘出“白气”,这是由于空气中的水蒸气遇冷液化而成的小水滴,故是液化,不符合题意;

C、秋天的露水是由于水蒸气遇冷液化而成的小水滴,故不符合题意;

D、冬天纷纷飘落的雪花,这是由于水蒸气遇冷直接形成的固态颗粒,故是从气态直接变为固态,即为凝华现象,故符合题意.

故选D.

多项选择题
阅读理解

阅读理解。

     Technology is the application (应用) of knowledge to production. Thanks to modern technology, we have

been able to increase greatly the efficiency of our work force. New machines and new methods have helped

cut down time and expense while increasing overall output. This has meant more production and a higher

standard of living. For most of us in America, modern technology is thought of as the reason why we can have

cars and television sets. However, technology has also increased the amount of food available to us, by means

of modern farming machinery and animal breeding techniques, and has extended our life span via (通过)

medical technology.

     Will mankind continue to live longer and have a higher quality of life? In large measure the answer depends

on technology and our ability to use it widely. If we keep making progress as we have over the past fifty years,

the answer is definitely yes. The advancement of technology depends upon research and development, and the

latest statistics (统计) show that the United States is continuing to pump billions of dollars annually (每年) into

such efforts. So while we are running out of some scarce resources (稀有资源) we may well find technological

substitutes (代用品) for many of them through our re- search programs.

     Therefore, in the final analysis the three major factors of production (land, labor and capital) are all influenced

by technology. When we need new skills, on techniques in medicine, people will start developing new technology

to meet those needs. As equipment proves to be slow or inefficient, new machines will be invented. Technology

responds to our needs in helping us maintain our standard of living.

1. What is the best title for the passage?

A. The way of technology.

B. Modern technology.

C. The application of technology.

D. The development of technology.

2. Which is the main idea of the passage?

A. Modern technology is the key to the improvement of standard of living.

B. The three major factors of production(land, labor and capital) are all influenced by technology.

C. Technology is the response to our needs.

D. The United States is making great efforts to advance its technology.

3. According to the passage, people can live a long life with the help of _____.

A. higher quality of life

B. medical technology

C. modern farming machinery

D. technological substitute