How Do Advertisers Exploit Reference Groups

How do advertisers exploit reference groups?

A) They offer group deals, so if you purchase the same item as a friend, you both get a discount.
B) They show images of people whom we hope to be like purchasing and using goods the advertisers are trying to sell.
C) They offer a discount on purchasing items in bulk, such as a "buy-one-get-one-free" deal.
D) They offer a trial subscription for free and then charge after the consumer has likely forgotten that they subscribed.