Final answer:
The defense mechanism the patient is displaying by refusing surgery and opting to decrease caffeine intake is Denial, where she refuses to accept the reality of the medical situation.
Step-by-step explanation:
When a physician recommends surgery for a breast mass and the patient refuses, choosing instead to decrease her caffeine intake, the defense mechanism she is displaying is A) Denial. Denial is the refusal to accept reality or fact, acting as if a painful event, thought or feeling did not exist. It is considered one of the most primitive of the defense mechanism because it is characteristic of early childhood development. The patient is denying the seriousness of the diagnosis and the physician's medical advice, and is instead opting for an alternative action that is unlikely to address the mass.