The upper half of an inclined plane of inclination q is perfectly smooth while the lower half is rough. A body starting from the rest at top comes back to rest at the bottom if the coefficient of friction for the lower half is given by [Pb. PMT 2000]

• A.             \[\mu =\sin \theta \]
• B.               \[\mu =cot\theta \]
• C.             \[\mu =2\cos \theta \]
• D.               \[\mu =\text{ }2\text{ }tan\theta \]