A、Advertisements are personal. B、Advertisements are convincing. C、Advertisements are unreliable. D、Advertisements are misleading

When you turn on the radio, you hear an advertisement. When you watch television, you hear and see an advertisement. If you turn the pages of a newspaper or magazine, again you find an advertisement. If you walk down the street, you see one advertising board after another. Every day, people who want to sell you something compete to catch your attention. As a result, advertisements are almost everywhere. In the West, advertisements are the fuel that makes mass media work. The government does not give money to mass media such as TV stations, newspapers, magazines and radio stations. They are all owned privately. 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 describe it in this way: Advertising is the paid, non-personal, and usually persuasive description of goods, services and ideas through various media.
   All advertisements try to make people believe that the product, idea or service advertised can do well to them. Advertisements exist everywhere in our lives.
Q:
16. What is the passage mainly about?
17. What’ s the financial source of the privately owned mass media?
18. According to the passage, what is one of the features of advertisements?