The correct answer is A) Oil in the drain inspection tank. This is the correct answer because the presence of oil in the drain inspection tank indicates a potential leak or malfunction in the machinery, which should be immediately reported to the engineering officer on watch. Drain inspection tanks are designed to collect any leaks or spills from the machinery, and the presence of oil in this tank signifies a problem that requires immediate attention. The other options, while potentially important issues, do not necessarily require immediate reporting to the engineering officer. Water trickling through the stern gland, steam leaving the vent of the gland exhaust condenser, and lube oil passing through the bull's eye of the gravity tank overflow line may be normal or expected occurrences that do not necessarily indicate an urgent problem.