Final answer:
The piece of legislation that states use to define and regulate the practice of physical therapy within their jurisdictions is known as the Practice Act (option C).
Step-by-step explanation:
The appropriate term for the piece of legislation that allows each state to define the progression of physical therapy and regulate its practice is C) Practice Act. States have autonomy to create their regulations concerning various professions, which is a reflection of the broader principle of state discretion over certain governance areas—a concept reinforced by legislative acts such as the Personal Responsibility and Work Opportunity Reconciliation Act of 1996. Besides legal regulations, it is important to note that physical therapists must also possess knowledge in physics to understand muscle contractions, energy release, and chemical reactions within the body, which are essential for making informed decisions in their practice.