A body takes time `t` to reach the bottom oa a smooth inclined plane of angle `theta` with the horizontal. If the plane is made rought, time taken now is `2t`.The coefficient of friction of the rough surface is
A. `(3)/(4) tan theta`
B. `(2)/(3) tan theta`
C. `(1)/(4) tan theta`
D. `(1)/(2) tan theta`