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  3. People often speak of fire as though it were a living creature—It grows, dances, needs oxygen, feeds on whatever it can find, an

People often speak of fire as though it were a living creature—It grows, dances, needs oxygen, feeds on whatever it can find, an

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问题     People often speak of fire as though it were a living creature—It grows, dances, needs oxygen, feeds on whatever it can find, and then dies. And when a forest fire rages out of control, threatening human lives and homes, it must be fought like a "wild animal. " The fight is often desperate, since firefighters’ best efforts may be dwarfed by the fury of a large fire. But the fire’s own traits can be used against it.
    The heated air above a fire rises in a pillar of smoke and burnt gases, pulling fresh air in from the sides to replace it. Firefighters use this fact when they "fight fire with fire. " They start a fire well in front of the one which they are fighting. Instead of traveling on in front of the huge fire, the smaller fire is pulled back toward it by the updrafts of the larger blaze. As it travels back to meet the large fire, the smaller backfire burns away the fuel that the forest fire needs to survive.
    Even when a backfire has been well set, however, the fire may still win the struggle. The wind which the firefighters used to help them may now become their enemy. When the backfire meets the main fire, before both die for lack of fuel, there is tremendous flame, great heat and wild winds. A strong gust may blow the fire into the treetops beyond the area, giving the fire new fuel and a new life.
A backfire is started______.
选项 A、behind a forest fire
B、ahead of a forest fire
C、on the sides of a forest fire
D、all around a forest fire
答案B
解析 第二段。In front of the huge fire表明在森林大火的前面。选项B是正确的。
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