Which of the Following Best Describes How Utilitarians Tend to Account

Which of the following best describes how Utilitarians tend to account for promises?

A) If one follows up on a promise, they produce happiness in the individual they're being faithful to
B) The practice of promise-keeping produces a lot of happiness, so we need to preserve trust
C) Violating an obligation always harms someone, so we must keep our promises
D) None of the above