A oil tanker may not discharge an oily mixture into the sea from a cargo tank, slop tank, or cargo pump room bilge unless which of the following conditions is present?

Correct Answer: Option D — discharging at an instantaneous rate of oil content not exceeding 30 liters per nautical mile

MARPOL Annex I and USCG regulations permit oily mixture discharges from cargo areas only when underway outside special areas, with an instantaneous rate of oil content not exceeding 30 liters per nautical mile, alongside operational oily-water separator controls.