Final answer:
Marty's behavior best illustrates the concept of displacement.
Step-by-step explanation:
Marty's behavior best illustrates the concept of displacement. Displacement is when someone transfers inappropriate urges or behaviors onto a more acceptable or less threatening target. In this case, Marty witnessed violence at home as a child, but instead of directing his anger towards his father, he hit children on the playground. As an adult, he continues to act violently towards his romantic partners, which is an example of displacement.