FCC Element 9 covers requirements set forth in IMO Assembly on Training for Radio Personnel (GMDSS), Annex 5 and IMO Assembly on Radio Maintenance Guidelines for the Global Maritime Distress and Safety System related to Sea Areas A3 and A4. The exam consists of questions from the following categories: radio system theory, amplifiers, power sources, troubleshooting, digital theory, and GMDSS equipment and regulations. To pass you must correctly answer at least 38 out of 50 questions.
Element 9 is a required written exam element for following FCC licenses:

GMDSS Radio Maintainer’s License (DM)
GMDSS Radio Operator/Maintainer License (DB)