A 30,000 DWT tankship is required to have an IOPP certificate when __________.

Correct Answer: Option D — calling at ports in another country signatory to MARPOL 73/78

MARPOL 73/78 Annex I requires an International Oil Pollution Prevention (IOPP) certificate for oil tankers of 150 gross tonnage and above, or other ships of 400 gross tonnage and above, when engaged in voyages to ports or offshore terminals under the jurisdiction of other parties to the Convention.