Which of These Statements Describes a Key Difference Between Advertising

Which of these statements describes a key difference between advertising and public relations?

A) Public relations is more expensive on a cost-per-contact basis than advertising.
B) Public relations is usually directly paid while advertising is usually indirectly paid.
C) Advertising is usually directly paid while public relations is usually indirectly paid.
D) Advertising provides an immediate feedback loop while public relations does not.
E) Public relations always has a much greater reach than advertising.