Which statement is true regarding passenger items during boarding?

The statement that all carry-on items must be secured is accurate because, during boarding, the safety and organization of the cabin are paramount. Secured carry-on items prevent potential hazards and ensure that the aisle and exits remain clear. This policy helps to maintain a safe environment for passengers and crew, as unsecured items can shift during flight or in emergency situations, creating risks for everyone on board.

In regards to the other statements, having restrictions on the number of items a passenger can carry or requiring that all bags be checked in does not align with most airline policies, where typically passengers are allowed one or more carry-on items depending on the airline’s regulations. Leaving items unattended is generally prohibited as it poses safety and security risks, potentially leading to disruptions during the boarding process.