A Child Is Having Temper Tantrums at Home, at School

Multiple Choice

A child is having temper tantrums at home, at school, and at his grandparents' house. After working with the parents for a while, the therapist believes that the child is being rewarded for his tantrums in each setting because his teacher, parents, and grandparents generally give him what he wants just to make him stop yelling. The therapist devises a plan to stop his tantrums but first implements the plan at home, then the following week at school, and finally at the grandparents' home several weeks later. From a research perspective, this is an example of

A) withdrawal method.
B) multiple baseline.
C) placebo control.
D) external validity.