The preventive measures for forest fires include some preemptive(抢先)methods that can help reduce the risks of fires and control their severity and spread，and thus,maintain ecological balance and protect 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 a 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 buildup，and clean up the fallen leaves，and thus，prevent the spread of forest fires to a vast area.Regular controlled burns can also help maintain 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，responsible human behavior can help reduce the number of forest fires to a great extent.In fact，we can reduce the number of wildfires dramatically by not leaving behind 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.Wildfires can increase the level of greenhouse gases(water vapor,carbon dioxide，etc)，and therefore increase 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 wildfires for their growth and reproduction.But large wildfires can cause extensive damage to the ecosystem，which again highlights the importance of effective control and prevention of forest fires·
　　1、The last paragraph tells us that __.
　　A.the greenhouse gases are caused mainly by wildfires
　　B.wildfires have both positive and negative effects
　　C.people should be aware of the necessity of wildfires
　　D.all the valuable trees disappear owing to wildfires
　　参考答案：B
　　参考解析：推理归纳题。该段介绍了林火的危害：affect climate and weather，increase the level of greenhouse gases，cause extensive damage to the ecosystem等;但也有积极的一面：they are also an important part of the ecosystem。所以B项客观得对forest fires做了表述。
　　2、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
　　参考答案：A
　　参考解析：主旨大意题。根据文章主题段第一段The preventive measures for forest fires include some preemptive(抢先)methods that can help reduce the risks of fires and control their severity and spread，and thus,maintain ecological balance and protect resources.可知文章从对林火的预防和发生后如何控制两方面做了介绍，所以A项最能全面概括文章内容。
　　3、A controlled forest fire may play a positive role because __.
　　A.a new forest will appear soon
　　B.it promotes the development of some seeds
　　C.nature keeps its balance only by wildfires
　　D.it makes the trees grow faster than before
　　参考答案：B
　　参考解析：细节理解题。从第二段“controlled burns can also help maintain biodiversity”以及最后一段“and many plants depend on the heat and smoke generated by wildfires for their growth and reproduction”得知在某种程度上很多植物从大火中得到了一定的好处。故B正确。
　　4、Firefighters get rid of all fuel in all 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
　　参考答案：D
　　参考解析：细节理解题。从文章第一段最后一句“…control the spread of a wildfire,firefighters usually create a control line by removing all fuel from an area so that the fire cannot travel across it.”得知消防人员清除掉所有的可燃物是为了阻止火势的蔓延。故D正确。
　　5、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 buildup and limit forest fires spread
　　D.provide reasonable conditions for some plants’growth
　　参考答案：C
　　参考解析：细节理解题。从第二段“…and thus,prevent the spread of forest fires to a vast area”得知政府这样做是为了阻止森林大火向其他地区的蔓延。故C正确。