The correct answer is D) Gravity tank overflow lines are lead directly to the lube oil sump. This is correct because in a gravity type lube oil system, the overflow from the gravity tanks is typically routed directly to the lube oil sump or reservoir. This ensures that any excess oil is safely returned to the system without causing any issues. The other answer choices are incorrect: A) is incorrect because a lube oil pump failure does not necessarily cause immediate damage to turbine bearings in a gravity type system, as the gravity tanks can still provide oil flow. B) is incorrect because gravity tanks are not typically fitted with overflow alarms, as the overflow is designed to directly return to the sump. C) is incorrect because the discharge from the gravity tanks flows directly to the lube oil pump suction, not the other way around.