The correct answer is B) At the GMDSS operating position. The GMDSS (Global Maritime Distress and Safety System) radio log must be kept at the GMDSS operating position on board the vessel. This is because the GMDSS log records all distress, urgency, and safety communications, as well as other critical radio traffic, and needs to be readily accessible to the GMDSS operator during watch-keeping duties. Keeping the log elsewhere, such as in the sea cabin, captain's office, or anywhere else on the vessel, would not meet the regulatory requirement for the log to be maintained at the GMDSS operating station. The other answer choices are incorrect as they do not comply with the proper location for the GMDSS radio log.