Final Answer:
A red or orange flag must be attached to the extreme end of the extension if driving in the daytime when a load extends 4 feet or more over the rear of a vehicle.
Step-by-step explanation:
When a load extends beyond the rear of a vehicle by 4 feet or more, it is essential to enhance visibility for other drivers on the road. To address this, a red or orange flag must be securely attached to the extreme end of the extension. This precautionary measure helps signal to surrounding motorists that there is an extended load, reducing the risk of accidents or collisions. The choice of red or orange is intentional, as these colors are easily noticeable and associated with warning signs, ensuring heightened awareness among fellow road users.