Explanation: The statement that is false is that a GMDSS maintainer may not be the person designated to have primary responsibility for radio communications during Distress incidents, even if licensed as an operator. In reality, a single individual can hold both a GMDSS maintainer endorsement and an appropriate GMDSS operator license (such as a GMDSS Radio Maintainer/Operator License or GMDSS Radio Operator License). If qualified as both, they absolutely *can* be designated for primary communications responsibility during distress. There is no regulation prohibiting one qualified person from fulfilling both roles simultaneously. Statements A, C, and D are all true: A) Ships are required to ensure GMDSS equipment maintenance through various means, including carrying at least one qualified GMDSS maintainer. C) All at-sea maintenance and repairs must indeed be performed or supervised by a person holding a valid GMDSS maintainer endorsement. D) A GMDSS maintainer, if also a qualified operator or officer, can certainly hold additional responsibilities, such as ensuring proper watchkeeping.