A link OB is rotating with a constant angular velocity of 2 rad/s in counter clockwise direction and a block is sliding radially outward on it with an uniform velocity of 0.75 m/s with respect to the rod, as shown in the figure below. If OA= 1m, the magnitude of the absolute acceleration of the block at location A in m/s2 is
(a) 3 (b) 4
(c) 5 (d) 6