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【单选题】
Directions: In this part, you will have 15 minutes to go over the passage quickly and answer the question on Answer Sheet 1. For questions 1-7, choose the best answer from the four choices marked A), B), C) and D). For questions 8-10, complete the sentences with the information given in the passage. ACID RAIN: What's the Solution? One of the wildest regions in the U.S., far from civilization, is the Adirondack area of northern New York State. For years this isolated spot has had the reputation of being one of the best fishing spots in the U.S. As a boy 30 years ago, Bill Marleau first tramped through the Adirondack wilderness near his small cabin on Woods Lake. Thousands of sportsmen have stayed at his father's lodge nearby. But now Bill's 134 hectares (335 acres) of lakefront land have only scenic value. Gone are those huge trout that used to swim in the turbulent, nutrient rich water a short distance from his doorstep. Gone from the cool summer nights are the sounds of thousands of frogs and toads. And gone are the birds that once fed on those water creatures. Occasionally Bill sees a lone fisherman fruitlessly cast his bait into the empty waters of old lake. "I just don't have the heart to tell them," he said. "This old lake's dead. It was killed years ago by acid rain." What Is Acid Rain Acid rain is a popular term for precipitation in the form. of rain, sleet, snow, or hail that is more acidic than normal. Acid rain is produced when atmospheric moisture combines with pollutants from power plants, factories, and automobiles. When fossil fuels such as coal and oil are burned, sulfur dioxide and nitrogen dioxide are produced. These two gases react with the water and oxygen in the atmosphere to form. droplets of weak sulfuric and nitric acids. Carried by prevailing winds and weather conditions, clouds containing these droplets travel hundreds, sometimes thousands of kilometers from the source of the pollutants. Recently scientists found that acid rain now affects huge areas of the Northern Hemisphere. Power plants and factories in the heavily industrialized regions of Ohio and Indiana are believed to be the source of the acid rain that killed Woods Lake along with hundreds of others in New York State and eastern Canada. Acid haze over Alaska is believed to come all the way from Japan. And precipitation as acidic as vinegar that falls on Scotland and Scandinavia probably originates in England. How Acidity Is Measured Scientists measure the acidity of rain in pH units. A pH scale from 0 to 14 is used. Depending upon its chemical composition, a solution is either acidic, alkaline (basic), or neutral. Distilled water, which has a pH of 7, is neutral. Substances with pH values less than 7 are acidic, while those with values over 7 are alkaline. Normal rain water with a pH of 5.6 is slightly acidic. But after reacting with industrial pollutants, particularly sulfur dioxide, the pH of rain quickly drops. When acid rain falls to Earth, much of it ends up in lakes and ponds. In addition to falling directly into a lake, acid rain runs off land into streams and rivers that eventually flow into lakes and ponds. Once acid rain gets into them, its effects can be deadly. Studies started in 1975 in the Adirondacks indicate that salamanders and frogs are the first to die when the pH is lowered. Normally the pH of a lake is 8.0: slightly alkaline. When the pH drops to 7, the eggs of salamanders and frogs fail to hatch. At pH 6.6 snails begin to die. Bacteria that decompose leaf matter die too, and the leaf matter collects on the take bottom. As the acidity continues to drop, all the major food chains in the lake become affected. In time all the fish die. Eventually primitive, oxygen-consuming plants nearly choke out all other aquatic greenery. Algae and fungal growth that thrive in an acidic environment move in and cover the entire bottom of the now destroyed lake. Looking like blue vinegar, the lake is now an entirely changed ecosystem. It contains no life except for the fungal and algal growth and a few surface dwelling water bugs. Acid rain also affects plants on land. The effects of acid rain on terrestrial vegetation are not as well documented or as clearly understood as its effects on lakes. Experiments by Ellis B. Cowling of North Carolina State University, however, indicate that acid rain destroys the natural waxy coating on tree leaves and fruits. This destruction makes the plants more susceptible to disease. Acid Rain Increasing The acid rain problem seems to be getting worse. According to the Environmental Protection Agency, the amount of sulfur dioxide from power plants, autos, and factories is four times greater than it was 25 years ago. And federal air pollution regulations don't seem to be helping as much as had been expected. One problem is that the Clean Air Act of 1977 established air pollution standards based on measurements made at ground level. Environmentalists claim that this action has encouraged polluters to spread airborne pollutants at higher elevations instead of eliminating them altogether. Tall smokestacks, often more than 100 stories tall, now spread sulfur dioxide close to water carrying clouds. Power company officials stress, however, that the tall stacks significantly reduce air pollution in areas near the power plants. And the officials also point to clean up efforts currently underway in the industry to reduce the amount of pollutants. New cleaner burning furnaces have been installed in recently constructed power plants. Scrubbers are also available that can be installed on industrial and power plant smokestacks. The scrubbers can remove up to 85 percent of the sulfur given off from stacks. Meanwhile, experiments continue in the development of cleaner sources of fuel such as low-sulfur, liquid coal. What can be done about lakes that are already acidic? Acidity can be reduced by dropping tons of lime (an alkaline substance) into the lake water. However, this solution is very expensive. Less optimistic scientists are trying to breed acid tolerant fish. These, measures, however are far from ideal. The solution to acid rain can only come from cooperation between industry, Government, and scientists. For what reason is the Adirondack area called one of the wildest regions in the US?
A.
Only primitive people live in the area.
B.
Acid rain has produced a deadly effect upon this region.
C.
The area has never been exploited for industrial purposes.
D.
Only wild animals are found in the area.
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参考答案:
举一反三
【单选题】关于运动终板的描述,哪一项错误
A.
是一种化学突触
B.
感觉神经纤维轴突末端到达肌纤维肌膜处失去髓鞘
C.
轴突到达肌纤维肌膜处反复分支,与肌纤维构成神经连接
D.
轴突终末富含突触小泡、线粒体和微丝
【判断题】国民生产总值已经扣除资本折旧的因素。
A.
正确
B.
错误
【单选题】学生信息表 Student 如下所示: 学号 姓名 性别 年龄 联系电话 所在省市 0001 李辉 男 18 1371212345 北京 0002 张明 男 18 13423236768 上海 0003 王小玉 女 17 13567891234 北京 0004 李淑华 女 19 13126357879 湖南 0005 赵静 女 20 13868687869 上海 ┆ ┆ ┆ ┆ ┆ ┆ 查询 每组...
A.
select 所在省市 ,AVG( 年龄 ) ' 平均 年龄 ' from Student group by 所在省市 having AVG( 年龄 )> 2 0 go
B.
select 所在省市 ,AVG( 年龄 ) ' 平均 年龄 ' from Student where AVG( 年龄 )> 2 0 group by 所在省市 go
C.
select 所在省市 ,AVG( 年龄 ) ' 平均 年龄 ' from Student compute by 所在省市 having AVG( 年龄 )> 2 0 go
D.
select 所在省市 ,AVG( 年龄 ) ' 平均 年龄 ' from Student order by 所在省市 go
【单选题】国民生产总值已经扣除资本折旧的因素。
A.
正确
B.
错误
【单选题】关于运动终板的描述中,那一项错误
A.
是一种化学性突触
B.
感觉神经纤维轴突末端抵达骨骼肌细胞时失去髓鞘
C.
轴突到达肌纤维肌膜处反复分支,与肌纤维构成神经肌连接
D.
轴突终末富含突触小泡
E.
肌膜即突触后膜,其上有受体
【单选题】学生信息表 Student 如下所示: 学号 姓名 性别 年龄 联系电话 所在省市 0001 李辉 男 18 1371212345 北京 0002 张明 男 18 13423236768 上海 0003 王小玉 女 17 13567891234 北京 0004 李淑华 女 19 13126357879 湖南 0005 赵静 女 20 13868687869 上海 ┆ ┆ ┆ ┆ ┆ ┆ 查询 男、...
A.
select 性别 ,MIN( 年龄 ) ' 最 小年龄 ',max( 年龄 ) ' 最大年龄 ' from Student compute by 性别 go
B.
select 性别 ,MIN( 年龄 ) ' 最 小年龄 ',max( 年龄 ) ' 最大年龄 ' from Student order by 性别 go
C.
select 性别 ,MIN( 年龄 ) ' 最 小年龄 ',max( 年龄 ) ' 最大年龄 ' from Student g o
D.
select 性别 ,MIN( 年龄 ) ' 最 小年龄 ',max( 年龄 ) ' 最大年龄 ' from Student group by 性别 go
【单选题】下列关于运动终板的描述中,错误的是
A.
轴突终末有突触小泡和线粒体
B.
是一种化学性突触
C.
突触小泡释放的乙酰胆碱可作用于突触后膜的N受体
D.
突触后膜上有受体
E.
是感觉神经元的轴突末梢
【单选题】关于运动终板的描述中,哪一项错误?
A.
是一种化学性突触
B.
感觉神经纤维轴突末端到达肌纤维肌膜处失去髓鞘
C.
轴突到达肌纤维肌膜处反复分支,与肌纤维构成神经肌突触
D.
轴突终末富含突触小泡、线粒体和微丝
E.
肌膜即突触后膜,其上有受体
【判断题】国民生产总值已经扣除了资本折旧的因素
A.
正确
B.
错误
【单选题】关于运动终板的描述,错误的是(  )
A.
由感觉神经元的神经终末与骨骼肌纤维共同形成
B.
突触后膜为肌膜
C.
突触小泡含有乙酰胆碱神经递质
D.
属于化学性突触
E.
又叫神经肌连接
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