Final answer:
The excerpt from Article II of the U.S. Constitution describes the president's military authority as commander in chief of the armed forces.
Step-by-step explanation:
The excerpt from Article II of the U.S. Constitution describes one of the president's major functions as the military authority. Specifically, it states that the president shall be the commander in chief of the Army and Navy of the United States, and of the militia of the several states when they are called into service. This role clearly fits under military authority, which is option C in the choices provided to the student.