The coefficient of friction between the block A of mass m and block B of mass 2 m is $\mu$. There is no friction between block B and the inclined plane. If the system of blocks A and B is released from rest and there is no slipping between A and B then

Question

a)$2 \theta \leq \cos^{-1} (2 \mu)$ b)$2 \theta \leq \sin ^{-1}(2 \mu)$ c)$2 \theta \leq \tan ^{-1} (\mu/2)$ d)$\theta \leq \tan^{-1}\mu$