Question EASA Drone License A2 - Flight performance and planning

278 - EASA Drone A2 License - When performing routine maintenance on a multirotor, what is the primary reason to check the brushless motors for physical resistance or 'grittiness' when spun by hand?

To ensure the magnets are properly polarized

To identify worn-out bearings or internal debris (like sand or salt) that could lead to a motor seizure and a catastrophic mid-air failure

To manually reset the internal Electronic Speed Controller (ESC) timing

To generate a small electrical charge to test the battery's health