Reading comprehension. A 10-year-old boy decided to study Judo( 柔道 ) despite the fact that he had lost his left arm in a car accident. The boy began his lessons with an old Japanese Judo teacher. The boy did well, but he could not understand why, after three months of training, the master had taught him only one move. "Master," the boy finally said, "Shouldn't I be learning more moves." "This is the only move you know, but this is the only move you will ever need to know," the master replied. Not quite understanding, but believing in his teacher, the boy kept training. Several months later, the master took the boy to his first tournament( 联赛 ). Surprising himself, the boy easily won his first two matches. The third match proved to be more difficult, but after some time, the opponent( 对手 ) became impatient and charged; the boy skillfully used his one move to win the match. Still amazed by his success, the boy was now in the finals. This time, his opponent was bigger, stronger and more experienced. For a while, the boy appeared to be outmatched. Concerned about the boy, the referee ( 裁判 )called a time-out. He was about to stop the match when the master came forward. "No," the master insisted, "let him continue." Soon after the match resumed, his opponent made a fatal mistake. He dropped his guard. Ins Instantnly. The boy used his move to pin him. The boy won the match. He was the champion. On the way home, the boy and the master reviewed every move in every match. Then the boy summoned the courage to asked what was really on his mind. "Master, how did I win the tournament with only one move?" "You won for two reasons," the teacher answered. "First, you've mastered( 掌握 ) one of the most difficult moves in Judo. And second, the only known defense( 防卫 ) for that move is to grasp( 抓住 ) your left arm. But you've lost it." The boy's biggest weakness had become his biggest advantage.