What Is the Difference Between the Primary Focus of Researchers

What is the difference between the primary focus of researchers and practitioners?

A) Researchers focus on changing individual's problematic behaviors by altering conditions in their environment. Practitioners conduct highly controlled experimental studies to determine the best behavior-change procedures to use with their clients.
B) Researchers try to discover relations between environment and behavior. Practitioners focus on improving lives.
C) Researchers work exclusively with nonhuman organisms to discover relations between the behavior and the environment that may generalize to human populations. Practitioners apply the research from nonhuman populations to their clients.
D) There is essentially no difference between the focus of researchers and practitioners.