单选题 .  Acting is such an overcrowded profession that the only advice that should be given to a young person thinking of going on the stage is "Don't!" But it is useless to try to discourage someone who feels that he must act, although the chances of his becoming famous are small. The normal way to begin is to go to a drama school. Usually only students who show promise and talent are accepted, and the course lasts two years. Then the young actor or actress takes up work with a play company, usually as assistant stage manager. This means doing everything that there is to do in the theatre: painting scenery, looking after the furniture, taking care of the clothes, and even acting in very small parts. It is very hard work indeed, the hours are long and the salary is tiny. But young actors with the stage in their blood are happy, waiting for the chance of work with a better company, or perhaps in films or television.
    Of course, some people have unusual chances which lead to fame and success without this long and dull training. Connie Pratt, for example, was just an ordinary girl working in a bicycle factory. A film producer happened to catch sight of her one morning waiting at a bus stop, as he drove past in his big car. He told the driver to stop, and he got out to speak to the girl. He asked her if she would like to go to the film company to do a test, and at first she thought he was joking. Then she got angry and said she would call the police. It took the producer twenty minutes to tell Connie that he was serious. Then an appointment was made for her to go to the company the next day. The test was successful. They gave her some necessary lessons and within a few weeks she was playing the leading part in a film, which made her well-known overnight throughout the country. Of course, she was given a more dramatic name, which is now world-famous. But chances like this happen once in a blue moon!1.  The main reason why young people should be discouraged from becoming actors is that ______.