The preventive measures for forest fires include some pre-emptive(抢先的)methods that can help re?duce the risks of fires and control their severity and spread,and thus, maintain ecological balance and pro?tect resources. Close monitoring of forest fires caused by natural factors can help prevent their spread to a large extent. To contain forest fires, fire departments usually use water and chemical fire retardants(抑制剂)that can be dropped from planes and helicopters. To control the spread of wildfire, firefighters usually create a control line by removing all fuel from an area so that the fire cannot travel across it.

Controlled burns are often employed by government authorities to reduce fuel build-up,and clean up the fall?en leaves,and thus,prevent the spread of forest fires to a vast area. Regular controlled burns can also help main?tain biodiversity(生物多样性),as the smoke and heat produced in the process can facilitate (促进)the growth of seeds of certain plant species. Apart from these, re?sponsible human behaviour can help reduce the number of forest fires to a great extent. In fact, we can reduce the number of wildfire dramatically by not leaving be?hind any source of fire in the forest.

Forest fires can affect climate and weather to a great extent, besides causing severe damage to valuable trees. Wildfire can increase the level of greenhouse gases (water vapour, carbon dioxide, etc. ) , and therefore in?crease pollution and global warming. However, they are also an important part of the ecosystem,and many plants depend on the heat and smoke generated by wildfire for their growth and reproduction. But large wildfire can cause extensive damage to the ecosystem, which again highlights the importance of effective control and pre?vention of forest fires.

1. Firefighters get rid of all fuel in an area in order to A.  keep close monitoring of forest fires

B.    prevent the forest fire from occurring

C.    protect the animals there

D.    stop the wildfire from spreading

2.    The government arranges some controlled burns to

A.    burn the rubbish and keep the forest clean

B.    help keep ecological balance of nature

C.    reduce fuel build-up and limit forest fires to spread

D.    provide reasonable conditions for some plants' growth

3.    The last paragraph tells us that      .

A.    the greenhouse gases are caused mainly by wild?fire

B.    wildfire has both positive and negative effects

C.    people should be aware of the necessity of wildfire

D.    all the valuable trees disappear owing to wildfire

4.    What may be the best title for this passage?

A.    Control and prevention of forest fires

B.    How to keep ecological balance

C.    Effects of forest fires

D.    Methods of fire spread control

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