It Has Been Suggested That Biofeedback Relieves the Pain of Tension

It has been suggested that biofeedback relieves the pain of tension headaches because it "teaches people to relax," but it is more likely that

A) the patients whose pain is seemingly relieved by biofeedback are probably also taking aspirin or Tylenol.
B) the biofeedback training gives patients a sense of control over their headache pain.
C) biofeedback has a "numbing effect" because it affects the nerve endings in the somatic nervous system.
D) patients experience a placebo effect, because the headache pain returns once the biofeedback sessions are completed.