Your examiner asks: "Tank cleaning after a Category Z cargo — what discharge conditions must be met to release tank washings at sea, compared with a Category Y cargo?"

A. Category Y washings may be discharged freely in port; only at-sea discharge is restricted.

B. There is no difference between categories for discharge purposes — all noxious liquid tank washings are subject to one universal discharge standard.

C. Category Z cargo washings may be discharged at any time regardless of ship speed or distance from land.

D. Category Z washings may generally be discharged under less restrictive concentration, distance-from-land and ship-speed conditions than Category Y; both still require the ship to be en route, proceeding at not less than a specified minimum speed, and outside any distance-from-land limit set by the IBC Code/Annex II for that category — Category X washings, by contrast, are generally not permitted to be discharged and must be retained or discharged to shore reception facilities.

A. Annex II categorises substances solely by flashpoint, with no relevance to discharge or tank-washing procedures.

B. Annex II only applies to crude oil carried in chemical tankers and uses the same Category A/B/C/D scheme as IMSBC.

C. Annex II regulates the carriage of noxious liquid substances in bulk and categorises them by hazard to marine resources/human health as Category X (major hazard, discharge prohibited), Y (hazard, discharge restricted by concentration/distance/speed), Z (minor hazard, less restrictive limits) and OS (Other Substances, evaluated as presenting no hazard, outside the Category X/Y/Z scheme).

D. Annex II applies only to substances also listed under the IMDG Code; substances not in IMDG are unregulated under Annex II.

A. The Cargo Record Book replaces the IOPP Certificate for chemical tankers and removes the need for an Oil Record Book.

B. A voluntary commercial log used only to record freight rates and demurrage, with no MARPOL legal status.

C. The Cargo Record Book is required only for Category X substances; Y, Z and OS cargoes have no equivalent recording obligation.

D. A mandatory record, analogous to the Oil Record Book, of every cargo and tank-cleaning operation involving noxious liquid substances — loading, internal transfer, unloading, tank washing/prewash, slop disposal, and discharge of residues — with dates, positions, quantities and the substance's category, retained for inspection by PSC.