Bruce has been feeling increasingly fatigued even if he exerts mildly. He discussed his condition with his neighbor, Sam, who also suffers from a similar problem. Sam told him that a mega dose of vitamin B complex is very helpful in eradicating the symptoms. Bruce tried Sam's remedy and found that his condition is gradually improving. This is an example of _____.

a. Placebo effect.
b. Homeostasis.
c. Psychosomatic healing.
d. Holistic therapy.