Suddenly , the helper guy changed the movie to another one .. with the first one remaining incomplete . A man who was very interested in the movie protested and asked the helper why he did so .. the helpers reply ... thrs a carbon deposit on the CD ... so it wo nt work . The man sat down without saying another word and i was smiling inside . Doctors are considered to be extremely intelligent people and i agree to that ... my father being one ... .but their intelligence fails when they work with something electronic . 
Question: Why did the helper guy change the movie to another one ?
There was a carbon deposit on the CD