At 2,315 miles (3,726 kilometres), the Missouri River is nearly as long as the Mississippi River, into which it flows. Together the Missouri and the Mississippi form one of the world's longest river systems.

There are seven major dams and dozens of smaller dams on the Missouri. The dams use water from the river to produce electricity. They also create reservoirs, or artificial lakes, behind them. The reservoirs store water that is needed for cities and for irrigation of crops. Irrigation is important because most of the regions around the river have fairly dry climate.

In addition to producing electricity, the dams on the Missouri are also used to control the water level of the river. Sometimes water is held back to prevent floods. At other times, water is released to keep the water level high enough for barges to float downstream.

By changing the natural flow of water in the Missouri, dams and reservoirs have altered the river's ecosystem. They have affected the depth and temperature of the water in different parts of the river. Such changes have made it difficult for some species, or types, of plants, animals, and fish to survive. A few wildlife species in the region are now endangered.

Câu 6:

On the Missouri River, there are dozens of _____.

A. major dams

B. small dams

C. reservoirs

D. crops

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Câu 7:

Why is it necessary sometimes to keep the water level high?

A. To produce electricity.

B. To prevent floods.

C. To let barges float downstream.

D. To change the flow of water.

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Câu 8:

The word "They" in the last paragraph refers to _____.

A. dams and reservoirs

B. parts of the river

C. such changes

D. some species

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Câu 9:

Which of the following is true, according to the passage?

A. The Missouri River is longer than the Mississippi River.

B. The Missouri River flows into the Mississippi River.

C. The Mississippi River flows into the Missouri River.

D. Wildlife species in the Missouri region are dangerous.

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Câu 10:

What is probably the best title for the passage?

A. Producing Electricity

B. Mississippi River

C. Dams on the Mississippi

D. Missouri River

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Đoạn văn 3

TASK 2. Read the passage and mark A, B, C, or D to indicate the correct answer that best fits each blank.

Mount Everest (Mt. Everest) is the highest mountain (1) the world. It is 8,848 metres high. Mt. Everest was first climbed in 1953 by Edmund Hillary and Tenzing Norgay. Every year, a lot of people want to climb Mt. Everest. It is very dangerous to climb Mt. Everest. The air is very (2) and cold. Most people carry bottles of oxygen; they could die without it. When the oxygen bottles are empty, people throw them on the ground. (3) strong winds rip their tents, people leave them behind. They do not have the energy to take the rubbish away. They only have enough energy to go down the mountain (4).

Rubbish is a terrible problem. Since people first began to climb Mt. Everest, they have left tons and tons of rubbish on the mountain. Several groups have climbed the mountain just to (5) the rubbish. When people plan to climb the mountain, they have to plan to take away their rubbish.

Câu 11: