Which of the Following Is an Example of Direct Marketing

Which of the following is an example of direct marketing?

A) a final consumer being exposed to a good or service through a Web-based ad
B) a final consumer being exposed to a good or service through a door-to-door salesperson
C) a final consumer being exposed to a good or service through a referral by a neighbor
D) a final consumer being exposed to a good or service through a referral by a department store's salesperson