Final answer:
Mary is in the 3. Action stage of the transtheoretical model of behavior change (TTM) because she has signed up for coaching sessions to help her reach her weight-loss goal.
Step-by-step explanation:
Based on the information given, Mary is currently in the Action stage of the transtheoretical model of behavior change (TTM). The TTM is a model that describes the process individuals go through when making behavior changes. The stages of the TTM include Contemplation, Preparation, Action, and Maintenance. In the Action stage, individuals have already started taking specific steps towards their behavior change goal. In Mary's case, she has signed up for coaching sessions with an ACE Certified Health Coach to help her reach her weight-loss goal, which indicates that she is actively engaged in taking action towards her goal.