2. Suppose a block is placed on a rough surface inclined relative to the horizontal and the coefficientof static friction between the block and the rough surface is μS. Let the incline angle be increasedfrom θ = 0 until the block starts to move. What is the critical angle θc at which this slipping justoccurs?
(A) θc= arctan(μS )
(B)θc= arccos(μS )
(C)θc=arcsin(μS )
(D)θc =π/2
(E) None of the above.