Heather hears a phone ring, then picks up the phone. Her husband talks with her over the phone. What is the behavior in this three-term contingency?

In a three-term contingency, the behavior is typically identified as the response that occurs as a result of a particular antecedent and leads to a consequence. In this scenario, the phone ringing serves as the antecedent, which prompts Heather’s specific behavior of picking up the phone.

Heather picking up the phone is an overt, observable action that represents her response to the environmental stimulus of the phone ringing. It is this behavior that directly connects the antecedent (the ringing phone) to the consequence (her husband talking to her).

The husband's conversation is a consequence that follows Heather’s behavior, and the act of receiving the phone call, while relevant, is not an individual behavior but rather denotes the overall process of the interaction. Thus, Heather's action of picking up the phone is the clear behavioral response in this three-term contingency framework, making it the correct choice.