[单项选择]The mixture of elements in the air can be thought ________ a solution of gases.


A. of as
B. of
C. as
D. of to

[单项选择]

There was one thought that air pollution affected only the area immediately around large cities with factories and heavy automobile traffic. At present, we realize that although these are the areas with the worst air pollution, the problem is literally worldwide. On several occasions over the past decade, a heavy cloud of air pollution has covered the east of the United States and brought health warnings in rural areas away from any major concentration of manufacturing and automobile traffic. In fact, the very climate of the entire earth may be infected by air pollution. Some scientists consider that the increasing concentration of carbon dioxide in the air resulting from the burning of fossil fuels(coal and oil) is creating a "greenhouse effect"—conserving heat reflected from the earth and raising the world’s average temperature. If this view is correct and the world’s temperature is raised only a few degree, much of the popular ice cap will melt and
A. shares the same view with the scientists
B. is uncertain of its occurrence
C. rejects it as being ungrounded
D. thinks that it will destroy the world soon

[单项选择]We can separate the mixture into the pure chemical compounds ______ it is composed.
A. in which
B. of what
C. of which
D. from which

[单项选择]Air is the mixture of gases in which （　） the gas is oxyen.
A. not every of
B. not all
C. none of
D. all of

[单项选择]That boys suffer more from air pollution can possibly be justified by the fact that ______.


A. the male have larger bones than the female
B. women can manufacture blood more efficiently than men
C. men usually breathe more deeply than women
D. women breathe as often as men

[单项选择]（　） man can now create radioactive elements, there is nothing he can do to reduce their radioactivity.
A. As
B. Whether
C. While
D. Now that

[单项选择]

Passage Four
Advertisement can be thought of "as the means of making known in order to buy or sell goods or services". Advertisement aims to increase people’s awareness and arouse interest. It tries to inform and to persuade. The media are all used to spread the message. The press offers a fairly cheap method, and magazines are used to reach special sections of the market. The cinema and commercial radio are useful for local market. Television, although more expensive, can be very effective. Public notices are fairly cheap and more permanent in their power of attraction. Other ways of increasing consumer interest are through exhibitions and trade fairs as well as direct mail advertisement.
There can be no doubt that the growth in advertisement is one of the most striking features of the Western World in this century. Many business such as those handling frozen foods, liquor, tabacco and medicines have been built up largely by advertisement.<
A. all the time
B. in any circumstances
C. in a growing market
D. in a shrinking market