Which pack is operative in the CREW OFF position?

In the context of the Dassault Falcon 7X, when the CREW OFF position is selected, the Main pack remains operative. This is a critical aspect of the aircraft's environment control system, designed to ensure that vital air conditioning and pressurization functionality is maintained for crew safety and comfort, even when the crew is not actively monitoring the systems.

The Main pack is specifically engineered to provide adequate cooling and air circulation within the cockpit and cabin, which is especially important in maintaining a safe operating environment. By having the Main pack continue to operate in the CREW OFF position, the aircraft ensures that essential environmental conditions are upheld.

The other options, such as the Emergency pack, APU pack, and Backup pack, have specific functions that do not directly support regular operations in the CREW OFF configuration. Therefore, while they might play roles during standard operations or in particular scenarios, their primary purpose does not include maintaining continuous operation during the CREW OFF setting, which is why they are not the correct answer.