The correct answer is C) discharge relief valve leaking back to the suction side. In a properly functioning refrigeration system, the high-pressure discharge side should have a higher pressure than the low-pressure suction side. If the discharge relief valve is leaking back to the suction side, it would allow high-pressure refrigerant to flow back into the low-pressure side, causing both low discharge and high suction pressures to occur simultaneously. The other options are incorrect because an overcharge of refrigerant (A) would cause high pressures on both sides, and a fouled condenser (B) or improper superheat adjustment (D) would typically result in high discharge and low suction pressures, not the combination described in the question.