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
浙江宁波2018八上第一次月考英语试题
湖南省长沙市稻田中2018下八第一次月考试题
2018陕西西安西安益新中学初二上学期月考英语试题
安徽省合肥新康中2018第一学期八第一次月考试题
2018陕西西安碑林区西铁初二上学期第一次月考英语试卷答案
浙江省杭州市三校2018第一学期八年级英语月考试题
2019-2020山东枣庄市中七年级上英语期末试题
2019-2020重庆万州七年级上英语期末试题答案
广西省昭平县第四中2018八年级上第一次月考试题
2019-2020安徽来安三城初中七年级上英语期末试题
2018陕西西安铁一中东城滨河中学上月考试题答案
常州市第24中2018第一学期八第一次月考试题
山东省青岛超银2018八年级上学期月考英语试题
浙江宁波2018八上第一次月考英语试题答案
浙江省嘉兴市2018八年级上学期月检测英语试题答案
2019-2020山东枣庄市中七年级上英语期末试题答案
安徽省合肥市第四十五中学2018八上第一次月考试题
甘肃会宁县韩集中八英语2018秋第一次月考试题
2019-2020安徽宣城七年级上英语期末试题答案
安徽省2018第一次月考八年级英语试卷()
吉大附中2018八英语上册5月月考试题
2018陕西西安碑林区西铁初二上学期第一次月考英语试卷
浙江省衢州市2018八上第一次月考英语试题答案
2019-2020山东枣庄峄城七年级上英语期末试题答案
浙江省杭州市三校2018第一学期八年级英语月考试题答案
2019-2020贵州贵阳普通中学七年级上英语期末试题
2019-2020河北唐山丰润七年级上英语期末试卷
山东省青岛超银2018八年级上学期月考英语试题答案
2019-2020山东青岛市北七年级上英语期末试题
安徽省阜阳市颍上三中2018第一学期第三次月考试题
不限 |
英语教案 |
英语课件 |
英语试题 |
不限 |
不限 |
上册 |
下册 |
不限 |