When fueling, where should crew member No4 be if the number of passengers is less than 150?

The correct choice indicates that crew member No4 should be positioned on board at the R1 door if they are not assisting passengers. This is aligned with safety protocols during the fueling process when the aircraft is on the ground and receiving fuel. The placement of a crew member at the R1 door ensures they are in a strategic location to monitor the boarding area while remaining prepared to assist with any emergencies or communications during fueling.

This positioning is particularly crucial when the passenger count is lower than 150, as it allows the crew member to maintain a presence on board without the need to engage actively with passengers. This enhances the safety and oversight of the aircraft during a critical phase of ground operations. It is important that at least one crew member remains in a position to assist should an emergency arise or should any issues occur during fueling.

Other options, while they might suggest that crew members are engaged in necessary tasks, do not align with the specific safety and monitoring requirements during aircraft fueling operations.