Dams are classified by the type of material used in their construction and by their shape．Dams call be constructed from concrete，stone，loose rock，earth，wood，metal，or a combination of these materials．Engineers build dams of different types，depending on the conditions of the riverbed and the surrounding landshape，and the construction materials．
Gravity dams use only the force of gravity to resist water pressure — that is，they hold back the water by the force of their weight pushing downward．They are much thicker at the base than the top —a shape that reflects the distribution(分布)of the forces of the water against the dam．As water becomes deeper，it puts more pressure on the dam．Gravity dams are relatively thin near the surface of the reservoir，where the water pressure is light．
An embankment dam is a gravity dam formed out of loose rock，earth，or a combination of these materials．
Arch dams are concrete or stone structures that curve upstream into a reservoir，requiting a relatively narrow fiver canyon(峡谷)with solid rock walls able to support a large amount of force．These dams do not need to be as massive as gravity dams because the canyon walls carry part of the pressure from the reservoir．Because．they require less material than gravity dams，arch dams can be less expensive to build．
A buttress dam consists of a wall，or face，supported by several buttresses every 6 to 30 meters on the downstream side．Buttress dams are sometimes called hollow dams because the buttresses do not form a solid wall stretching across a fiver valley．It falls into two basic kinds：flat slab and multiple arches．Flat slab buttress dams have a flat upstream face．Multiple arch buttress dams have an upstream face formed by a series of arches．
Like arch dams，buttress dams require less concrete than gravity dams，but they are not necessarily less expensive to build than gravity dams．Costs with the work of forming the buttresses or multiple arches may offset(抵消)the savings in construction materials．Buttress dams may be desirable，however，in locations with foundations that would not easily support the massive size and weight of gravity dams．
1．Which of the following pictures best stands for gravity dams?
2．According to the passage，it generally costs less to build _______．
A．arch dams than gravity dams B．buttress dams than gravity dams
C．gravity dams than arch dams D．gravity dams than buttress dams
3．Which of the following would be preferred to build in places with foundations not strong enough?
A．Gravity dams． B．Arch dams．
C．Buttress dams． D．Embankment dams．
4．The best title for this passage would be _________．
A．Functions of Dams B．Constructions of Dams
C．Costs of Dams D．Types of Dams
寒假乐园北京教育出版社系列答案科目：高中英语 来源： 题型：阅读理解
Australia －a huge island continent that lies to the south of Asia. Australia－more than two hundred years old, a nation that is still growing.
Its big cities lie on the southeast coast, this is where most Australians live. Australians prefer to own their own houses, though some live in apartments. Australians are a suburban（郊区的） people. The suburbs surround the cities for many miles, and so efficient transport is of great importance. As the economy grows, so do its industries- a higher level of production, a wider range of products.
The Australian works hard, but he likes his leisure. The climate makes outdoor activities the most popular.
Canberra, the capital of Australia, is a planned modern city located inland. Australia is governed by a parliamentary democracy(议会民主). The representatives of other countries have their embassies here. Australia wants to strengthen relations with her neighbors.
Australia is a strange land
, a land of vast expanses- fertile valleys, snow fields and deserts- also a land with unique animal, many that can not be found on any other continent in the world today.
Much of the continent is dry, but man has utilized the land, made it productive, with its tools, with its technology. This is the driest continent of all, and water is a precious possession, more precious than all other natural resources. Large dams are built to collect the water, there to irrigate the fields of pastures（牧场） and crops.
But Australia is changing. The land of wool and wheat is now 
a land of large-scale industry and mining. The costs of developing the new mineral discoveries are enormous, but the rewards are great too.
Australia — a young and developing nation. Australia — a nation that wants to communicate with its neighbors. .w.^w.k.&s.5*u.c.#om.
Australia is an island located ______ of Asia and its big cities lie ____ of the coast.
A. to the south; on the southeast B. to the north; on the southwest
C. to the east; on the northeast D. to the east; on the southwest
We can infer from the passage that the Australian likes outdoor activities for the _____ climate.
A. dull and wet B. fine and shiny C. gloomy and rainy D. wet and cold
____ is the most precious source in Australia.
A. Mineral resource B. Animal C. Desert D. Water
Which of the following statements about Australia is wrong?
A. Australians are a suburban people
B. Australia is governed by a parliamentary democracy.
C. Australia prefers to live in the downtown of big cities.
D. Wool and wheat used to be the main products of Australia. .w.^w.k.&s.5*u.c.#om.
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科目：高中英语 来源：2011—2012学年甘肃省天水市三中高三级第五次检测考试英语试卷 题型：阅读理解
From the beginning rivers have played an important in the life of man．Man of the earliest times used the rivers as a means of travel．Today rivers still serve as a great waterway for the transport and people．
In ancient times, man settled near rivers or on river banks and built up large empires．
Water is nature’s most valuable gift to man．Man needs water to irrigate his crops, to cook and to wash．In nations all over the world, rivers mean life and wealth．They feed and clothe the nations around them．
Water is also a source of energy and power．Man build huge dams across the rivers to control the water for irrigation and get the energy needed to drive generators．The electrical power is then directed to homes, cities, factories and television stations．
Man uses water each day．In a small way rivers help to keep man in good health and provide for his amusements．Various forms of water sports keep man strong and healthy．
【小题1】Rivers have been important to man _______．
| A．since they came into being | B．since the last century |
| C．since a few hundred years ago． | D．since the beginning of BC |
| A．by air | B．by sea | C．by train | D．by bus |
| A．to direct electrical power | B．to control the water |
| C．to produce electricit | D．to build dams y |
| A．People get energy by building bridges across rivers． |
| B．In ancient times large empires grew up near dams． |
| C．People can be provided with amusements in small rivers． |
| D．Large rivers are still useful for transportation in modern times． |
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科目：高中英语 来源：2012届陕西省澄城县寺前中学高三第四次月考英语试卷 题型：阅读理解
Australia －a huge island continent that lies to the south of Asia．Australia－more than two hundred years old, a nation that is still growing．
Its big cities lie on the southeast coast, this is where most Australians live．Australians prefer to own their own houses, though some live in apartments．Australians are a suburban people．The suburbs surround the cities for many miles, and so efficient transport is of great importance．As the economy grows, so do its industries- a higher level of production, a wider range of products．
The Australian works hard, but he likes his leisure．The climate makes outdoor activities the most popular．
Canberra, the capital of Australia, is a planned modem city located inland．Australia is governed by a parliamentary democracy．The representatives of other countries have their embassies here．Australia wants to strengthen relations with her neighbors．
Australia is a strange land, a land of vast expanses- fertile valleys, snow fields and deserts- also a land with unique animal, many that can not be found on any other continent in the world today．
Much of the continent is dry, but man has utilized the land, made it productive, with its tools, with its technology．This is the driest continent of all, and water is a precious possession, more precious than all other natural resources．Large dams are built to collect the water, there to irrigate the fields of pastures and crops． But Australia is changing．The land of wool and wheat is now a land of large-scale industry and mining．The costs of developing the new mineral discoveries are enormous, but the rewards are great too．
Australia — a young and developing nation．Australia — a nation that wants to communicate with its neighbors．
【小题1】Australia is an island located ______ of Asia and its big cities lie ____ of the coast．
| A．to the south; on the southeast |
| B．to the north; on the southwest |
| C．to the east; on the northeast |
| D．to the east; on the southwest |
| A．dull and wet |
| B．fine and shiny |
| C．gloomy and rainy |
| D．wet and cold |
| A．Mineral resource | B．Animal | C．Desert | D．Water |
| A．Australians are a suburban people |
| B．Australia is governed by a parliamentary democracy． |
| C．Australia prefers to live in the downtown of big cities． |
| D．Wool and wheat used to be the main products of Australia． |
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科目：高中英语 来源：2011-2012学年陕西省高三第四次月考英语试题 题型：阅读理解
Australia －a huge island continent that lies to the south of Asia．Australia－more than two hundred years old, a nation that is still growing．
Its big cities lie on the southeast coast, this is where most Australians live．Australians prefer to own their own houses, though some live in apartments．Australians are a suburban people．The suburbs surround the cities for many miles, and so efficient transport is of great importance．As the economy grows, so do its industries- a higher level of production, a wider range of products．
The Australian works hard, but he likes his leisure．The climate makes outdoor activities the most popular．
Canberra, the capital of Australia, is a planned modem city located inland．Australia is governed by a parliamentary democracy．The representatives of other countries have their embassies here．Australia wants to strengthen relations with her neighbors．
Australia is a strange land, a land of vast expanses- fertile valleys, snow fields and deserts- also a land with unique animal, many that can not be found on any other continent in the world today．
Much of the continent is dry, but man has utilized the land, made it productive, with its tools, with its technology．This is the driest continent of all, and water is a precious possession, more precious than all other natural resources．Large dams are built to collect the water, there to irrigate the fields of pastures and crops． But Australia is changing．The land of wool and wheat is now a land of large-scale industry and mining．The costs of developing the new mineral discoveries are enormous, but the rewards are great too．
Australia — a young and developing nation．Australia — a nation that wants to communicate with its neighbors．
【小题】Australia is an island located ______ of Asia and its big cities lie ____ of the coast．
A．to the south; on the southeast
B．to the north; on the southwest
C．to the east; on the northeast
D．to the east; on the southwest
【小题】We can infer from the passage that the Australian likes outdoor activities for the _____ climate．
A．dull and wet
B．fine and shiny
C．gloomy and rainy
D．wet and cold
【小题】____ is the most precious source in Australia．
A．Mineral resource B．Animal C．Desert D．Water
【小题】Which of the following statements about Australia is wrong?
A．Australians are a suburban people
B．Australia is governed by a parliamentary democracy．
C．Australia prefers to live in the downtown of big cities．
D．Wool and wheat used to be the main products of Australia．
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科目：高中英语 来源：2010-2011学年河南省高三上学期第一次月考英语卷 题型：阅读理解
Australia －a huge island continent that lies to the south of Asia. Australia－more than two hundred years old, a nation that is still growing.
Its big cities lie on the southeast coast, this is where most Australians live. Australians prefer to own their own houses, though some live in apartments. Australians are a suburban（郊区的） people. The suburbs surround the cities for many miles, and so efficient transport is of great importance. As the economy grows, so do its industries- a higher level of production, a wider range of products.
The Australian works hard, but he likes his leisure. The climate makes outdoor activities the most popular.
Canberra, the capital of Australia, is a planned modern city located inland. Australia is governed by a parliamentary democracy(议会民主). The representatives of other countries have their embassies here. Australia wants to strengthen relations with her neighbors.
Australia is a strange land, a land of vast expanses- fertile valleys, snow fields and deserts- also a land with unique animal, many that can not be found on any other continent in the world today.
Much of the continent is dry, but man has utilized the land, made it productive, with its tools, with its technology. This is the driest continent of all, and water is a precious possession, more precious than all other natural resources. Large dams are built to collect the water, there to irrigate the fields of pastures（牧场） and crops.
But Australia is changing. The land of wool and wheat is now a land of large-scale industry and mining. The costs of developing the new mineral discoveries are enormous, but the rewards are great too.
Australia — a young and developing nation. Australia — a nation that wants to communicate with its neighbors.
1.Australia is an island located ______ of Asia and its big cities lie ____ of the coast.
A. to the south; on the southeast B. to the north; on the southwest
C. to the east; on the northeast D. to the east; on the southwest
2.We can infer from the passage that the Australian likes outdoor activities for the _____ climate.
A. dull and wet B. fine and shiny C. gloomy and rainy D. wet and cold
3.____ is the most precious source in Australia.
A. Mineral resource B. Animal C. Desert D. Water
4.Which of the following statements about Australia is wrong?
A. Australians are a suburban people
B. Australia is governed by a parliamentary democracy.
C. Australia prefers to live in the downtown of big cities.
D. Wool and wheat used to be the main products of Australia.
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