Category Y Noxious Liquid Substances are those that, if discharged during tank cleaning or deballasting, pose hazards to marine resources, human health, or coastal amenities. Because of that risk, discharges are not allowed freely; they must be kept within limits that control both how concentrated the substance is in the effluent (quality) and how much is released (quantity). This reflects MARPOL Annex II’s approach to hazard-based discharging: extreme hazards are prohibited outright, while less severe hazards require restrictively managed discharges. So the correct choice highlights the need for a limitation on both the quality and quantity of the discharge. The idea of complete prohibition applies to the most hazardous Category X substances, saying there is no hazard would be wrong for Category Y, and being outside Annex II would ignore the regulatory framework governing these discharges.