Functional Equivalence Is Best Described as What

Functional equivalence is best described as what?

A) All behaviors a person exhibits are linked with a corresponding trait of the person.
B) Traits are best described in terms of their behavior; therefore behavior must be the focus of the study of traits.
C) People consist of a small number of traits that can be used to describe all behavior.
D) Many situations are viewed by people as similar in meaning, so they respond similarly; the trait is the internal structure that causes this regularity.
E) Traits are underlying structures that people are born with and are in no way related to the different behaviors that people exhibit.