Question id 27 - Preflight Procedures - FAA PPL(A) - Private Pilot Airplane

Only the Pilot-in Command must have fastened a seatbelt and shoulder harness.
All persons in an airplane must have a seatbelt and shoulder harness fastened.
Only front seat passengers must have fastened a seatbelt and shoulder harness.

Training tests and timed exam simulations FAA PPL(A) - Private Pilot Airplane