A、Because it was too heavy. B、Because it did not bend easily. C、Because its string was short. D、Because it did not shoot far. D题

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 short bow was used by nearly all early people.[19]This bow had limited power and a short range. However, man overcame these faults by learning to track his targets at close range.[20]The long bow was most likely discovered when someone found out that a five-foot piece of wood made a better bow than a three-foot 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 bow was just a bent stick and string. In fact, more changes have taken place in a bow in the last 25 years than in the last 7 centuries.[21]Today’s bow is forceful. It is as exact as a gun. In addition, it requires little strength to draw the string. Modern bows also have precise aiming devices. In indoor contests, perfect scores from 40 yards are common. The invention of the bow itself ranks with discovery of fire and the wheel. It was a great step forward for man.
19. Why did man have to track his targets at close range when using a short bow?
20. What does the passage tell us about the long bow?
21. What do we know about modern bows?