Which documents are required to be onboard the airplane?

The correct answer includes the essential documents that must be onboard an aircraft to ensure compliance with aviation regulations. The Airworthiness Certificate signifies that the aircraft has been inspected and deemed safe for operation; it must be displayed in the aircraft. The Registration proves that the aircraft is registered with the appropriate authority, providing proof of ownership and ensuring accountability. The Operating Handbook, also known as the Pilot Operating Handbook (POH), provides critical information about the aircraft’s performance, limitations, and operational procedures.

Having these documents readily available is crucial for both legal and operational reasons. They ensure that the pilot and any relevant personnel can verify the aircraft's airworthiness, understand its operating limitations, and reference necessary procedures during flight. Therefore, option B accurately reflects the mandatory documents required onboard an airplane.