How do public relations and advertising differ?

a. Advertising is about selling an organization; in public relations, it's about selling products and services.

b. There virtually is no difference between the two.

c. Public relations strives for unbiased, objective, third-party messengers to relay information about an organization as well as its products and services; in advertising, the choice of media helps accomplish that.

d. Advertising focuses on paying for time or space that allows advertisers to disseminate their organization's messages about its products and services; in public relations, credibility helps to earn media recognition.