Completing a written contract to modify an unhealthy behavior serves to

This serves to provide a start date to take action. It is because when a person makes a written contract in modifying the unhealthy behavior that an individual acquires, this will serve as the basis and the one responsible for making an individual to start considering or reminding the individual of changing his or her actions or to start to take action with the particular behavior.

i am pretty sure it is d.

im sorry i wish i can but try google