单选题
It didn't happen overnight. The problem of polluted
air has been festering for centuries. Suddenly the problem of
air pollution is becoming critical and is erupting right before our eyes. Not
only do our eyes bum as they focus through murky air, but when the air clears,
we see trees and vegetation dying. We must realize that this destruction can no
longer be pinned to some mysterious cause. The one major culprit is air
pollution. Today's air pollution is an unfortunate by-product
of the growth of civilization. Civilized mall desires goods that require heavy
industrialization and mass production. Machines and factories sometimes pollute
and taint the air with substances that are dangerous to man and the environment.
These substances include radioactive dust, salt spray, herbicide and pesticide
aerosols, liquid droplets of acidic matter, gases, and sometimes soil particles.
These materials can act alone to irritate objects and forms of life. More
dangerously, they join together to act upon the environment. Only lately have we
begun recognizing some of their dangerous consequences.
Scientists have not yet been able to obtain a complete report on the effects of
air pollution on trees. They do know, however, that sulfur dioxide, fluorides,
and ozone destroy trees and that individual trees respond differently to the
numerous particulate and gaseous pollutants, Sometimes trees growing in a single
area under attack by pollutants will show symptoms of injury or will die while
their neighbors remain healthy. Scientists believe this difference in response
depends on the kind of tree and its genetic makeup. Other factors, such as the
tree's stage of growth and nearness to the pollution source, the amount of
pollutant, and the length of the pollution attack also play a part. In short,
whether or not a tree dies as a result of air pollution depends on a combination
of host and environmental factors. For the most part, air
pollutants injure trees. To conifers, which have year-round needles, air
pollution causes early balding. In this event, trees cannot maintain normal food
production levels. Undernourished and weakened, they are open to attack by a
host of insects, diseases, and other environmental stresses. Death often
follows. Air pollution may also cause hardwoods to lose their
leaves. Because their leaves are borne only for a partion of the year and are
replaced the following year, air pollution injury to hardwoods may not be so
severe.
单选题
The author attributes today's air pollution to ______.
A. the growth of civilization
B. man's carelessness
C. environmental imbalance
D. some mysterious cause
【正确答案】
A
【答案解析】[解析] 题目问：作者把今天的空气污染归因于什么？第二段“Today's air pollution is an unfortunate by product of the growth of civilization,”通过这句话可知，当今的空气污染是人类文明发展过程中的一个不良副产品。据此判断，应选择A。
单选题
The resistance of some trees to disease can be traced to ______.
A. protective foliage
B. thick bark
C. genetic makeup
D. tainted air
【正确答案】
C
【答案解析】[解析] 题目问：树木对疾病的抵抗可以追溯到什么？第四段“Scientists believe this difference in response depends on the kind of tree and its genetic makeup,”通过这句话可知，科学家认为，树木对疾病的不同反应取决于树的种类和遗传因素。据此判断，应选择C。
单选题
Air pollution causes the most damage to ______.
A. hardwoods
B. conifers
C. fruit trees
D. fluorides
【正确答案】
B
【答案解析】[解析] 题目问：空气污染对什么树木的损害最大？第五段“To conifers,...and other environmental stresses. Death often follows.”第六段“air pollution injury to hardwoods may not be so severe.”通过这句话可知，空气污染对树术有影响，针叶林往往会死掉，但对阔叶林的损害就不那么严重。据此判断，应选择B。
单选题
The author implies that the greatest source of pollution is ______.
A. heavy industry
B. chemical processing plants
C. urban expansion
D. salt spray
【正确答案】
A
【答案解析】[解析] 题目问：作者暗示，最大的污染源是什么？第三段第二句“Civilized mall desires goods that require heavy industrialization and mass production.”通过这句话可知，生产商品需要熏工业的支持，伴随而来的就是环境污染。据此判断，应选择据此A。
单选题
We can conclude that ______.
A. air pollution is easier to control than water pollution
B. the problem of polluted air is a problem overnight
C. the impact of air pollution has been known for centuries
D. research on the efforts of air pollution is incomplete
【正确答案】
D
【答案解析】[解析] 题目问：通过文章内容我们可以得出什么结论？第四段第一句“Scientists have not yet been able to obtain a complete report on the effects of air pollution on trees.”通过这句话可知，关于空气污染对树木的影响问题，科学家还没有得到完整的结论。据此判断，应选择D。