Step-by-step explanation:
Public relations are the relations a company make with the public. Such events include the direct contact of the company with the public. Whereas Sales Promotions are the events that are held by a company to promote their sales. Sales promotions and Public relations Events are often held by the companies to remain in spotlight.
In this question the given events are asked to classify as either Public Relations or Sales Promotions. So they are classified as follows:
Contests Public Relations
Product Samples Sales Promotions
Charity Events Public Relations
Giveaways Sales Promotions