A、Because he did something wrong and was punished for that. B、Because his father wanted to give him a chance to show his talent

Mozart was born on January 27, 1756 and died on December 5, 1791. When he was three, he often had lessons with his elder sister. His father took him through many different countries where he played music for lots of people.
   But some people did not believe that a little boy could write such beautiful music. They asked him to stay in a room all by himself for a week and somebody watched the room all the time. In the week, he finished a new piece of music. After that, people believed that he could write beautiful music.
   Mozart died when he was still a young man. During his short life he studied music, taught music, played music and wrote music. Even by working so hard, he couldn’t make much money. Often he had to borrow money from his friends. But his music made him happy, and for more than two hundred years, his music has made many other people happy.