A、They do not harm anyone. B、They usually look more frightening. C、They cause damage to buildings or bridge. D、They are much les

Have you ever seen a movie in which a building was burnt down or a bridge was destroyed? Have you seen films ill which a train crashed or a ship sank into the ocean? If so, you may have wondered howthese things could happen without harming the people in the film.
    The man who knows the answer is the special effects man. He has one of the most important jobs in the film industry. He may be ordered to create a flood, or to make a battlefield explode. But he may also be asked to create a special effect. It is much more exciting.
    Once a film director wanted some fish that were swimming in a big glass bowl to stop swimming suddenly while they were seen to stare at an actor. Then the director wanted the fish to stop staring and swim away. But fish can’t be ordered to do anything. It was quite a problem. The special effects man thought about this for a long time. The result was an idea for controlling the fish with the harmless use of electricity. First he applied electricity to the fish bowl causing the fish to be absolutely still. Then he rapidly reduced the amount of electricity allowing the fish to swim away. Thus he got the humorous effect that the director wanted.