A block is at rest on an inclined plane making an angle `alpha` with the horizontal . As the angle `alpha` of the incline is increased the block starts slipping when the angle of inclination becomes `theta`. The coefficient of static friction between the block and the surface of the inclined plane is or A body starts sliding down at an angle `theta` to the horizontal. Then the coefficient of friction is equal to
A. `sin theta`
B. `cos theta`
C. `tan theta`
D. Independent of `theta`
