The correct answer is D. Operator access to control functions among the various ROS locations differ depending on system configuration and need. This is because in a distributed automation system, the different ROS (remote operating system) workstations may have varying levels of access and control permissions based on their intended purpose and the system design. The master ROS is not necessarily located in a specific area like the ship's office or wheelhouse. The access and control capabilities of each ROS are configured to meet the operational requirements and needs at that particular location. The other options are incorrect because A and B assume a fixed master ROS location, while C assumes identical access across all ROS locations, which is not necessarily the case in a distributed system.