Final answer:
A certified, licensed supervisor must always remain on-site with a non-certified employee when using restricted-use pesticides.
Step-by-step explanation:
A certified, licensed supervisor must always remain on-site with a non-certified employee when using restricted-use pesticides. This is because restricted-use pesticides are highly regulated and require a trained professional to handle them safely. The presence of a certified, licensed supervisor ensures that the non-certified employee follows proper protocols and minimizes the risk of accidents or mishandling of the pesticides.