A、They are filled with advertisements. B、They are interrupted by advertising messages. C、They must be interesting to huge groups

Public television in America grew out of the many local stations that broadcast educational programs in the 1950s. In 1967 Congress passed the Public Broadcast Act. The goal of this law was to provide educational programs for all Americans. There is a major difference between public television and commercial television. (26)Commercial television programs are paid for by companies that advertise their products or services during the program. Public television programs do not have such advertising messages. Another difference is that commercial television is pressured by advertisers to broadcast programs popular with huge groups of people. These include comedies and game shows. Public television does not face such pressures. (27)It can broadcast programs of interest to smaller groups of people. These programs are often more unusual, creative and experimental than programs broadcast on commercial television.
     Public television in America presents many kinds of programs. There are news and opinion programs. There are films about social and historical events. And there are shows about science and nature. (28)There are shows to teach people how to cook, grow vegetables or fix a house. There are many drama programs produced in Britain．And there are programs that present the music, dance and theater of America.
     So many local American people enjoy the public television, most of the time, they spent the day or their leisure time on it and also got the information from the programmes.