1. The problem asks for the radian measure of one of the 12 equal central angles in a circle. 2. The total angle around a point (circle) is $2\pi$ radians. 3. Since the circle is divided into 12 equal parts, each central angle is given by the formula: $$\text{Central angle} = \frac{2\pi}{12}$$ 4. Simplify the fraction: $$\frac{2\pi}{12} = \frac{\cancel{2}\pi}{\cancel{12}6} = \frac{\pi}{6}$$ 5. Therefore, the radian measure of any one of the 12 equal central angles is $\frac{\pi}{6}$ radians. Final answer: D) $\frac{\pi}{6}$ radians