听力原文： At first Muhammad Ali-Cassius Clay had no intention of boxing. After his bike was stolen, in the month of October 1954, when he was twelve, his whole life destiny changed in an instant. Ali exclaimed a 'state-wide bike hunt'. A police officer who heard this offered Ali lessons in how to box in order to beat up the thief. This was the starting point in Muhammad Ali's boxing career. In the late fifties, Cassius Clay ruled Golden Gloves and the AAU national champion. A quick fight at the Rome Olympics in 1960, Cassius Clay beat a Polish fighter to a 'bloody pulp' and took home the gold. In 1962 Muhammad Ali knocked out Archie More in the fourth round as he predicted. In 1964, Muhammad Ali became world heavy weight champion by beating Sonny Listen. However, he did not fight for three and a half years when he was standing up forhis rights during the Vietnam War. He said, 'I have no Quarrel with Vier Cong.' He did not want to fight because the more troops we sent in, the more we lost. His reason for not going in was religious beliefs. They stripped him of his world title, fined him ten thousand dollars, and sentenced him to 5 years in prison. In 1970, he returned to the ring, when he was granted a boxing license. And he began to win lots of championships in the following decade. But his career ended with a ten-round victory over Trevor Berbick in 1981．Later that year Ali began suffering symptoms of Parkinson's disease． Muhammad Ali started to learn boxing because______.