On which side of the aircraft are the oxygen overboard indicator and service panel located?

The oxygen overboard indicator and service panel are installed on the left side of the aircraft. This location is critical as it aligns with design parameters and the operational needs of ground personnel and emergency responders. By having these indicators on the left side, it allows for better visibility and easier access during routine checks and in case of emergencies. This design choice is commonly found across various aircraft types, ensuring consistency for maintenance teams and contributing to overall safety protocols. The other options do not accurately reflect the aircraft's design and operational layout, reinforcing the left side's designation as the correct answer.