Daniella Invited Nicole to Her House for a Party, Which

Daniella invited Nicole to her house for a party, which turned out to be a sales pitch for the cosmetic line that Daniella had recently started selling. Nicole didn't need any cosmetics, but since she was already at Daniella's house and enjoying the complimentary food and drink, she felt obligated to purchase some lipstick. Daniella is using the:

A) foot-in-the-door technique.
B) door-in-the-face technique.
C) rule of reciprocity.
D) highball technique.