In modern times, many powerful insecticides have been used in an attempt to destroy insects that damage crops and trees. Some kinds of insecticides, when carefully used, have worked well. Yet the same insecticides have caused some unexpected problems. In one large area, an insecticide was used against Japanese beetles, which eat almost any kind of flower or leaf. Shortly afterward, the number of corn borers almost doubled. As intended, the insecticide had killed many Japanese beetles. But it had killed many of the insect enemies of the corn borer as well.
In another case, an insecticide was used in Louisiana to kill the troublesome fire ant. The insecticide did not kill many fire ants. It did kill several small animals. It also killed some insect enemies of the sugarcane borer, a much more destructive pest than the fire ants. As a result, the number of sugarcane borers increased and severely damaged the sugarcane crop.
To be sure that one insect pest will not be traded for another when an insecticide is used, scientists must perform careful experiments and do wide research. The experiments and research provide knowledge of the possible hazards an insecticide may bring to plant and animal communities. Without such knowledge, we have found that nature sometimes responds to insecticides in unexpected ways.
21. An insecticide was used in Louisiana to kill the troublesome______.
A. corn borer B. Japanese beetle
B. gypsy moth D. fire ant
22. While it is not directly stated, the article suggests that______.
A. insecticides are not dangerous to any small animals
B. insecticides do not always accomplish their purposes
C. insecticides are no longer being used to kill insects
D. insecticides do no harm to people
23. On the whole, the article tells about______.
A. the appetites of plant-eating insects B. the best way to kill boll weevils C. the dangers in using insecticides D. the best way to grow crops
24. Which statement does this article lead you to believe?
A. All changes are predictable. B. Nothing ever changes in nature.
C. Nature is not always predictable. D. Nature always serves man well.
25. Scientists perform careful experiments and do wide research because______.
A. they must learn to destroy all the insects that we need
B. they must be sure one insect pest is not traded for another
C. research keeps them from inventing new insecticide for the crops
D. research helps them find a way to kill all insects
21. D 22. B 23. C 24. C 25. B
2016年中考英语词组辨析:at Christmas/ on Christmas
2016年中考英语词组辨析:as soon as/ hardly…when/ no sooner…than
2016年中考英语词组辨析:always/often/frequently/usually/sometimes
2016年中考英语词组辨析:before long/ long before
2016年中考英语词组辨析:as well as/ as well
2016年中考英语词组辨析:awake/ wake/ waken
2016年中考英语词组辨析:as soon as/ as early as/ as quickly as
2016年中考英语词组辨析:all/ every
2016年中考英语词组辨析:almost/ nearly
2016年中考英语词组辨析:although/ though
2016年中考英语词组辨析:at/ beside/ by/ near
2016年中考英语词组辨析:as/ because/ for/ since
2016年中考英语词组辨析:animal/ beast
2016年中考英语词组辨析:at first/ first
2016年中考英语词组辨析:asleep/ sleep / sleepy
2016年中考英语词组辨析:edge / side
2016年中考英语词组辨析:besides/ but/ except/ beside/ except for
2016年中考英语词组辨析:all/ whole
2016年中考英语词组辨析:at times / at all times / all the time
2016年中考英语词组辨析:at/ in
2016年中考英语词组辨析:be amazed at (by) / be amazed to do sth
2016年中考英语词组辨析:alone/ lonely
2016年中考英语词组辨析:be afraid to do sth/ be afraid +that clause
2016年中考英语词组辨析:beach/ bank/ coast/ shore
2016年中考英语词组辨析:allow/ permit/ let/ promise
2016年中考英语词组辨析:at/ to
2016年中考英语词组辨析:arms/ weapon
2016年中考英语词组辨析:among/ between/ in the middle of
2016年中考英语词组辨析:arise/ rise
2016年中考英语词组辨析:always / yet
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