(B, C) False: The net acceleration of a particle in circular motion is not always directed along the radius of the circle toward the centre. This is only true for uniform circular motion. In non-uniform circular motion,there is also a tangential component of acceleration.
$(b)$ True: At any point on a curved path,the instantaneous velocity is directed along the tangent to the path at that point.
$(c)$ True: In uniform circular motion $(UCM)$,the acceleration vector is the centripetal acceleration,which always points toward the centre. As the particle moves,the direction of this vector changes continuously. The vector sum of these centripetal acceleration vectors over one complete cycle is zero,making the average acceleration a null vector.