Final answer:
In the transtheoretical model, the Preparation stage is when an individual plans to make changes, recognizing that they have a problem and committing to addressing it.
Step-by-step explanation:
The stage of the transtheoretical model where a person realizes that they have a problem and plans to make changes to their behavior is Preparation. At this stage, individuals intend to take action in the immediate future, and usually have already taken some significant action in the past year. People in this stage also recognize that they have a problem and begin to make a commitment to solving it.