What is the purpose of Annex II hazard categories X, Y, Z in Noxious Liquid Substances, and how do they guide tank cleaning?

• A. They indicate preferred ports for NLS shipments.
• B. They categorize NLS severity; cleaning requirements escalate with category, with X being the most stringent.
• C. They describe the color of NLS labels.
• D. They specify ship crew nationality.

Answer: (B)