What statement is true concerning oil-lubricated stern tube bearings?

Correct Answer: Option D — The forward and after seals are both designed to retain the lubricating oil within the bearings and the after seal is designed to prevent the ingress of sea water.

Oil-lubricated stern tube installations utilize multiple sealing rings where the forward seal retains internal lubricating oil and the after seal prevents both oil leakage outward and seawater ingress inward.