Professor Yates Is Lecturing on the Definition of Psychology

Professor Yates is lecturing on the definition of psychology.Which example of "behavior" should he use to most effectively communicate the definition?

A) "Behavior consists of activities such as thinking, forgetting, and problem-solving."
B) "Acts such as eating, walking, and running are examples of behavior."
C) "Behavior is synonymous with internal processes like memory and learning."
D) "We make no distinction between the observable and the unobservable-anything that a person does is behavior."