As jay was asked by his therapist to talk about his resentment toward his wife, jeff quickly changed the subject by telling a joke. this scenario demonstrates

This scenario demonstrates resistance.

Resistance refers to when a patient or a client is reluctant or not willing to talk about a particular topic in therapy. For example if a client is not comfortable talking about his father, he may demonstrate resistance when any information about his father is asked and can even change the subject of his discussion with the person. From the question, the scenario demonstrates resistance.