A、Threat from weapons. B、Influence of violence on TV. C、Changes of moral principles. D、The unknown reason. BWhat is the cause of

During the past decade, there has been a rapid increase in violent crimes throughout the work. Not only has there been a frightening increase of murders, but also chances of being attacked and robbed have grown. Many old people avoid leaving their apartments.
    The exact cause of this horrifying development has not been found. Some researchers think that the growth of crime on TV is related to the growth of violence on streets. Others blame the constant threat of complete destruction from nuclear explosions. If the world is going to be blown up, why not enjoy yourself fully!
    Regardless of the cause or causes, a fundamental change in attitude among people is easy to see. Years back, the old saying "Practice what you preach" was a popular one. People had moral standards they could follow: concern about their fellow human beings.
    Today people have become "l-centered". They are more interested in pursuing immediate and selfish pleasures. The best advice they can give is "Do what I say, not what I do." They are saying, "There are moral principles to follow if you want to, but don’t use me as a guide since I no longer follow them."