During an emergency, what indication follows after the cabin door is armed on the ERJ 175?

When the cabin door is armed on the ERJ 175, it is configured to prepare for an emergency evacuation. In this state, the door's operating mechanism is modified so that it can be opened immediately in an emergency situation. The arming process usually involves the deployment of the slide, which is intended to assist passengers in evacuating the aircraft quickly and safely. This means that once the door is armed, it does not require any additional actions for it to be opened; it is ready for immediate use.

The other options focus on conditions or methods that are not applicable in this emergency context. For instance, manual or electronic opening suggests a delay or complication that would not be suitable in a rapidly evolving emergency scenario. Thus, option D is correct because the armed state of the cabin door ensures the crew can open it without further steps, facilitating an efficient exit for all on board.