A、Because it takes much time, and it increases the cost of the product or service. B、Because the cost of materials is high. C、Be

Advertisement is the difficult business of bringing information to great numbers of people. The purpose of an advertisement is to make people respond to an idea, such as helping prevent forest fires, or to make them want to buy a certain product or service. (16)At the beginning of the 20th century, advertisement was described as “salesmanship in print”. If this definition were expanded to include radio and television, it would still stand today. The most effective way to sell something is through person-to-person contact. (17)But the cost of person-to-person selling is high because it takes a great deal of time, and it increases the cost of the product or service. Advertising distributes the selling message to many people at one time. (18)The first printed advertisement in the English language appeared in 1278, more than a century before Shakespeare’s first play was produced. This early advertisement was the work of William Caxton, England’s first printer, who used it to advertise religious books from his own workshop. Caxton posted small printed notices along London’s main streets. Besides advertising his product, he identified his shop with a red-striped shield so that customers could find it easily. This same sort of simple informational advertising is still used. Examples are the roadside signs that tell travelers that they can buy fresh corn just down the road or that there is a restaurant in the next town.
Questions 16 to 18 are based on the passage you have just heard.
16.When was advertisement described as “salesmanship in print”?
17.Why is the cost of person-to-person selling high?
18.When did the first printed advertisement in the English language appear?