The correct answer is D. All vessels under the Global Maritime Distress and Safety System (GMDSS) as defined by the International Maritime Organization (IMO) must be capable of performing the following communications functions: distress alerting to and from vessels, search and rescue coordination, on-scene communications, signals for locating, Maritime Safety Information, and general and bridge-to-bridge communications. The other options are incorrect because A) does not cover all the required GMDSS functions, B) is too specific to the International Safety-NET service, and C) refers to a different capability (radio direction finding) not included in the core GMDSS requirements.