The circular measure of the included angle formed by the hour hand and minute hand of a clock at 3 p.m. will be

Answer: Option D

The hour hand of a watch traces an angle of 30° in an hour.
∴ Angle traced at 3 O' clock = 3 × 30° = 90°
$$\begin{array}{rl}& \because 180^{\circ }=\pi \text{ radian}\\ & \therefore 90^{\circ }=\frac{\pi }{180}\times 90^{\circ }=\frac{\pi }{2}\text{ radian}\end{array}$$