Match the block diagrams of block of mass, m, with their corresponding free body diagram.
(Bodies are at rest with respect to ground)
P - (ii); Q - (ii); R - (iv); S - (ii)
Only forces are gravity and normal force applied by the ground on the block
Same as above as the block is at rest and there is no horizontal force applied on it and friction opposes relative motion
In this case, block b also applies a normal force Nb on m in the downward direction
(S) The last case is again equivalent to the first case.