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  3. The first automobile was invented more than two hundred years ago. It used steam for power and had wooden wheels. The first auto

The first automobile was invented more than two hundred years ago. It used steam for power and had wooden wheels. The first auto

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问题     The first automobile was invented more than two hundred years ago. It used steam for power and had wooden wheels. The first automobile may have been simple and primitive, but it was an extremely important invention. The automobile today is the primary means of land transportation. It has produced more changes in our daily life than any other machines.
    Almost all gasoline engines work in the same way—with four movements, or strokes, of a piston in a cylinder. The first stroke pulls the fuel mixture (gasoline and air) into the cylinder. The second stroke compresses the fuel mixture. A spark plug produces a spark that ignites the fuel mixture and causes the third stroke. The final stroke removes any waste gases which might remain in the cylinder.
    The preceding paragraph explains what happens inside the cylinder to make the piston move. When the piston is pushed down by the explosion in the third stroke, it pushes the connecting rod. This rod rotates the crankshaft. The crankshaft is connected to other parts which turn the wheels. Most cars today have four, six, or eight cylinders.  
Fuel enters the cylinder in the ______.
选项 A、first stroke
B、second stroke
C、third stroke
D、the final stroke
答案A
解析 本题属细节题。文章第二段第二句中的“the first stroke pulls the fuel”已提示答案。
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