What is the first action taken before conducting an outside inspection?

Before conducting an outside inspection, the first action required is to remove the seatbelt and exit the vehicle. This is a critical safety measure that ensures the operator is outside the bus and has a clear view of the vehicle's exterior components, which need to be inspected for safety and functionality.

Exiting the vehicle allows the operator to begin the pre-trip inspection by checking items such as the tires, lights, and overall condition, all of which are essential for ensuring the bus is safe to operate. If the operator remains inside the bus, they cannot perform the necessary visual inspections effectively.

The other options, while important safety checks, pertain to different moments in the pre-trip process. For instance, closing the bus door securely should be done after entering the bus and before starting the inspection inside, and ensuring passengers are seated properly is a concern once the vehicle is in motion, not prior to conducting the inspection. Starting the engine to check indicators is typically done after the exterior inspection, not before.