The correct answer is D) The larger sized regulating rings are designed to be used with oils of lower specific gravities. The reasoning is that for a centrifugal separator to maintain a constant separating temperature, the size of the regulating ring needs to be adjusted based on the specific gravity of the oil. Oils with lower specific gravities require larger regulating rings to achieve the desired separating temperature, while oils with higher specific gravities need smaller regulating rings. This is because the size of the regulating ring impacts the flow rate and residence time of the oil in the centrifuge, which in turn affects the separating temperature. The other options are incorrect because A) is the opposite of the correct relationship, B) is not accurate as the specific gravity and regulating ring size are related during operation, not just initial design, and C) is incorrect as higher viscosity oils do not require smaller regulating rings for constant temperature operation.