The correct answer is C) The solenoid valve closes, allows the water in the opening chamber to bleed off through "S", and the sliding piston moves upward due to the force developed in area "J". This is the correct answer because when the solenoid valve closes, it stops the high-pressure water from entering the opening chamber. This allows the water in the opening chamber to bleed off through the "S" port, reducing the pressure in that chamber. The force developed in area "J" then causes the sliding piston to move upward, terminating the sludge discharge cycle. The other options are incorrect because they do not accurately describe the mechanism that terminates the sludge discharge cycle. Option A describes the valve opening to initiate the cycle, not terminate it. Options B and D do not accurately explain the forces and pressure changes that lead to the upward movement of the sliding piston.