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 h
A. faster than a horse can run
B. in all directions at the same speed
C. in whatever direction the wind is blowing
D. toward the nearest source of fuel
| 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 A. how fires start B. damage caused by fire C. the fascination of fire D. fighting forest fires [单项选择]How often one hears children wishing they were grown up, and old people wishing they were young again. Each age has its pleasures and its pains, and the happiest is the one who enjoys what each age gives him without wasting his time in useless regrets.
Childhood is a time when there are few responsibilities to make life difficult. If a child had good parents, he is fed, looked after and loved, whatever he may do. In addition, life is always presenting new things to the child things that have lost their interest for older people because they are too well known. A child finds pleasure in playing in the rain, or in the snow. His first visit to the seaside is a marvelous(非凡的) adventure. But a child has his pains., he is not so free to do as he wishes as he thinks older people are; he is continually being told not to do things, or being punished for what he has done wrong. His life is therefore not perfectly happy. When the young man starts to earn his own loving, he becomes free A. children from families B. young men who are healthy and wealthy C. old people who have been successful D. those who enjoy the goodness of each age 我来回答: 提交
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