Final answer:
The concept best described in the scenario is Self-regulation. Mary knows that she needs to complete her chores before her friend can come over, so she demonstrates self-regulation by finishing her tasks first.
Step-by-step explanation:
The concept best described in the scenario is Self-regulation. Self-regulation refers to the ability to control one's behavior, emotions, and impulses in order to achieve a goal or meet expectations. In this case, Mary knows that she needs to complete her chores before her mother will allow her friend to come over. By completing her chores first, Mary is exhibiting self-regulation by managing her tasks and responsibilities.