Final answer:
A) Displacement. The client in this scenario is demonstrating the defense mechanism of Displacement.
Step-by-step explanation:
The client in this scenario is demonstrating the defense mechanism of Displacement after being accused of stealing by their boss. Displacement occurs when a person transfers their inappropriate urges or behaviors onto a more acceptable or less threatening target. In this case, the client directs their anger and frustration towards working out at the gym instead of confronting their boss directly.