2021年西北工业大学网络教育大学英语练习题（6）

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Passage One

You’ve likely been told by your parents not to play with fire. Fire can be dangerous.

However, some fires are very healthy and helpful to our planet.

Until the 20th century, almost all forest fires were naturally occurring fires, started by natural means, such as lightning strikes. These fires are a part of our ecosystem. When forest fires occur naturally, they tend to move quickly through the forest. They burn the lower branches and clear the deadwood and weeds from the forest floor.

For many years, the US government tried to prevent as many forest fires as possible. As a result, forests build up layers of deadwood and brush. This left forests at risk for much fiercer natural fires. The extra deadwood served as fuel. It also kept forests less healthy for trees and wildlife.

Forest fires improve the forest as a habitat for large trees that prefer some open space. In addition, forest fires help seeds begin to grow. Some types of trees only let go of seeds when they are exposed to great heat. These natural fires also remove sick plants and harmful insects from a forest ecosystem.

In recent years forest-management techniques have changed. Scientists understand the importance of fire to the forest. Forest agencies have begun starting controlled fires. These help remove the growth that has built up over so many years. At the same time, people have increased their use of the forest for leisure purpose. Now most forest fires are caused by human carelessness. People being careless with matches or cigaretts can start fires.  Sometimes people leave their campfire unattended. These fires often cause more damage than natural fires because they upset the balance of nature. They also can destroy timber and harm the soil.

Always be careful when you are camping or walking through the woods. Be careful with matches and make sure campfires have been put out properly. We will all see the benefits from these precautions in our forests and natural environments.

31.What do we know about naturally occurring fires?

A.They help cure sick plants.

B.They are important to forest.

C.They keep seeds from growing.

D.They disturb the balance of nature.

32.The US government’s efforts in preventing forest fires in the past ______.

A. proved to be useful B. benefited wildlife a lot

C.stopped natural fires from occurruing.

D.affected the development of forests

33.In the last few years, US forest agencies started to ______.

A.forbid people to camp in the forest

B.understand the harm of forest fires

C.use fire to clear the forest floor

D.be worried about forest fires

34.The word “precaution” in the last paragraph probably means ______.

A. measures B. instructions C. disasters D. researches

答案

31-34 B D D A

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