In the West, advertisements are the fuel that makes mass media   work. Many TV stations, newspapers, magazines, radio stations are privately owned. The government does not give them money.  So where does the money come from?  From advertisements. Without advertisements, there would not be these private businesses. Have you ever asked yourself what advertising is? Through the years, people have given different answers to the question. For some time it was felt that advertising was a means of "keeping your name before the public". And some people thought that advertising was "truth well told". Now more and more people consider it in this way: Advertising is the paid, non-personal, and usually persuasive presentation of goods, services and ideas by some certain sponsors   through various media. First, advertising is usually paid for. Various sponsors pay for the advertisements we see, read, and hear over the various media. Second, advertising is non-personal. It is not face-to-face communication. Although you may feel that a message in a certain advertisement is aimed directly at you, in fact, it is directed at large groups of people. Third, advertising is usually persuasive. Directly or indirectly it asks people to do something. All advertisements try to make people believe that the product, idea, or service advertised can benefit them. Fourth, the sponsors of the advertisement must show their names. From the advertisement, we can see if the sponsor is a company, or a single person. Fifth, advertising reaches us through old and modern mass media. Included in the old media are newspapers, magazines, radio, television, and films. Modern media include emails, matchbox covers, and boards on top of buildings. The passage seems to say that different ideas about what advertising is are given due to    _   .
the change of time the subject of the advertisements people's age difference people's different opinions