单项选择题
A 30，000 DWT tanker is required to have an IOPP certificate when（）
A.engaged in the coastwise trade B.going foreign C.calling at ports in another country signatory to MARPOL 73/78 D.carrying cargoes listed in the MARPOL regulations
单项选择题 Before welding can be done in a tank that has carried petroleum products，a certificate must be obtained from（）.
