单选题The burning of the fuel adds more heat to the air charge, causing it to expand and force the engine piston to do work on the crankshaftWhat does “it” mean in this sentence?（）Athe burningBthe fuelCthe air chargeDthe engine piston
单选题
The burning of the fuel adds more heat to the air charge, causing it to expand and force the engine piston to do work on the crankshaftWhat does “it” mean in this sentence?（）
A
the burning
B
the fuel
C
the air charge
D
the engine piston
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In the experiment, the burning inside the bottle can___.A. equalize the air pressure inside and outsideB. make a seal in the neck of the bottleC. finish up the oxygen inside the bottleD. produce more oxygen inside the bottle
Passage ThreeHow can we get rid of garbage.9 Do we have enough energy sources to meet our future energy needs?These are two important questions that many people are asking today. Some people think that man might be able to solve both problems at the same time. They suggest using garbage as an energy source, and at the time it can save the land to hold garbage.For a long time, people buried garbage or dumped it on empty land. Now, empty land is scarce. But more and more garbage is produced each year. However, garbage can be a good fuel to use. The things in garbage do not look like coal, petroleum, or natural gas; but they are chemically similar to these fossil fuels. As we use up our fossil-fuel supplies, we might be able to use garbage as an energy source. Burning garbage is not a new idea. Some cities in Europe and the United States have been burning garbage for years. The heat that is produced by burning garbage is used to boil water. The steam that is produced is used to make electricity or to heat nearby buildings. In Paris, France, some power plants burn almost 2 million metric tons of the cities garbage each year. The amount of energy produced is about the same as would be produced by burning almost a half million barrels of oil.Our fossil fuel supplies are limited. Burning garbage might be one kind of energy source that we can use to help meet our energy needs.44. What two problems can man solve by burning garbage?A. The shortage of energy and air pollution.B. The shortage of energy and the land to hold garbage.C. Air pollution and the shortage of fossil fuel.D. Air pollution and the shortage of land to hold garbage.
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