In an Important Research Study Involving Elderly Nursing Home Residents

In an important research study involving elderly nursing home residents, psychologists Judith Rodin and Ellen Langer investigated the:

A) effects of relaxation techniques on psychological and physical health.
B) psychological effects but not the physical effects, of regular exercise.
C) effects of a sense of personal control on psychological and physical health.
D) effects of a stress-reduction training program on blood pressure and immune system functioning.