Final answer:
The restriction regarding contact information in an advertisement is that it must be accurate and truthful, and advertisers cannot make false or misleading statements.
Step-by-step explanation:
The restriction regarding contact information in an advertisement is that it must be accurate and truthful. Advertisers are allowed to use a certain amount of exaggeration to promote their products or services, but if they present a claim as a fact, it must be true. In other words, they cannot make false or misleading statements. For example, if an advertisement claims that a certain product can cure a specific disease, but it cannot actually do so, it would be considered false and misleading.