题目

Advertising is a highly developed twentieth-century industry. The development of radio, television, cinema, magazines and newspapers has gone hand in hand with the development of advertising. Why is advertising so popular? Is it a waste of money? It has been proved again and again that repeated advertising increases product sales. Since it increases production, the price can be reduced. Therefore advertising, instead of making a product more expensive, makes it cheaper. Advertising is now a scientific business. Once managers would say jokingly, I know that half of what I spend on adver地壳中含量最多的金属元素是（　　） A．硅               B．氧               C．铝               D．铁