听力原文： Bows and arrows are one of man's oldest weapons. They gave early man an effective weapon to kill his enemies. The ordinary bow or shoat bow was used by nearly all early people. This how had limited power and short range. However, man overcame these faults by learning to track his targets at a close range. The long how was most likely discovered when someone found out that a fivefoot piece of wood made a better bow than a threefood piece. Hundreds of thousands of these bows were made and used for three hundred years. However, not one is known to survive today. We believe that a force of about one hundred pounds was needed to pull the string all the way back on a long bow. For a long time the how was just a bent stick and string. In fact, more changes have taken place in a bow in the past 25 years than in the last 7 centuries. Today, bow is forceful. It is as exact as a gun. In addition, it requires little strength to draw the string. Modem bows also have precise aiming devices. In indoor contest, perfect scores from 40 yards are common. The invention of the bows itself ranks with discovery of fire and the wheel. It was a greatstepforward for ream.
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A. Because it was too heavy.
Because it did not bend easily.
C. Because it did not shoot far.
D. Because its string was short.