You Walk into a Classroom to Find the Word Adaptation

You walk into a classroom to find the word adaptation written on the board. It appears that the instructor was using a diagram to show that adaptation involves a balance between two factors, one of which is what people do or want to do. What is the other factor?

A) what people fail to do
B) what the environment requires
C) feelings of accomplishment related to what people are doing
D) hereditary predispositions that lead people to act in certain ways