The postulates that individuals engaging in a new behavior, such as adopting a regular exercise program, move through the stages of precontemplation, contemplation, preparation, action, and maintenance.

The transtheoretical model of behavior change postulates that individuals engaging in a new behavior, such as adopting a regular exercise program, move through the stages of precontemplation, contemplation, preparation, action, and maintenance.

Explanation:

The transtheoretical model of behavior change was developed in 1977. It is a result of analysis and application of several psychotherapy theories - hence the name "transtheoretical". Its purpose is to assess someone's readiness to change an unhealthy behavior, trading it for a healthier one. The stages are:

1. Precontemplation

2. Contemplation

3. Preparation

4. Action

5. Maintenance

6. Termination

The stages vary from: a person not being ready to change a harmful behavior at all --> the person thinking of the possibility and beginning to admit his behavior is unhealthy --> the person taking small steps toward change and intending to do it for good --> the person modifying their behavior openly --> the person keeping the new behavior going for over six months --> the person feeling no temptation to return to the previous harmful behavior.

i would have to say "a" or "d".