Which One of the Following Is an Example of an Operational

Which one of the following is an example of an operational definition of a concept?

A) Aggression is any behavior that results in physical or emotional injury to a person.
B) Aggression is threatening, biting, gossiping, or teasing somebody.
C) There are four kinds of aggression: accidental, expressive, instrumental, and hostile.
D) Accidental aggression occurs when someone is hurt in the process of play or social interaction: stepping on someone's fingers while climbing the monkey bars.