One of the truisms of the advertising industry is that it is rarely necessary to say something of substance in an advertisement in order to boost sales. Instead， one only needs to attract the potential customer‘s attention; memory does the rest， for it is more important for sales that people know of a product than that they know something about it.
Which of the following is assumed by the argument?
People can remember a product without having much information about it.
Advertisements， in their own way， function to improve people’s memories.
Attracting a potential customer‘s attention is a simple matter.
The advertising industry knows little of substance about the products it promotes.
Advertisements seldom tell the truth about a product.