What must be verbally confirmed with an instructor before entering the aircraft?

Verbal confirmation that all safety pins are installed before entering the aircraft is crucial for ensuring safety during the operation. Safety pins are employed to prevent unintended movement of critical components, such as the ejection seat and other emergency systems, while the aircraft is on the ground. If any of these pins are not correctly installed, it could result in serious safety risks during pre-flight checks, taxiing, or takeoff. Therefore, confirming their proper installation with an instructor ensures that the aircraft is in a safe configuration before the pilot boards.

The other choices, while also important for flight safety and preparation, do not carry the same immediate implications for pilot safety during entry into the aircraft. Fuel levels, flight plans, and weather conditions can all be checked and confirmed in various ways and do not necessarily require an instructor's verbal confirmation right before entering the aircraft.