The correct answer is: (c) The spring is at its maximum extension.
Work Step by Step
Initially, the only force acting on the mass is gravity since the spring is in its relaxed position. When the mass reaches the equilibrium position, the upward force exerted by the spring is equal in magnitude to the weight. Then the net force is zero so the acceleration is zero. At the lowest point, gravity exerts a downward force while the spring exerts an upward force. Since the spring's upward force is greater in magnitude than the weight, the mass has its maximum acceleration directed upward at the lowest point when the spring is at maximum extension. The correct answer is: (c) The spring is at its maximum extension.