Final answer:
The central angle of a circle measures the amount of rotation needed to go from one radius to another along the circumference of the circle. In a complete circle, the central angle is 360°.
Step-by-step explanation:
The central angle of a circle is the angle formed by two radii originating from the center of the circle. It measures the amount of rotation needed to go from one radius to the other along the circumference of the circle. Since a circle has 360 degrees, the correct answer for the central angle is d. 360°.