Final answer:
To check for gas fumes after fueling a PWC, you should smell for fumes. Striking a match is extremely dangerous as it could ignite the fumes.
Step-by-step explanation:
The best way to check for gas fumes after fueling a Personal Watercraft (PWC) is by smelling for fumes. Gas vapors can be detected by the sense of smell, which is more reliable in this scenario than visual inspection or listening for sounds. It is important to note that you should never strike a match or create a spark near fuel vapors as this could cause ignition and result in a fire or explosion.