What does the sign of a left U-turn stop indicate?

The sign indicating a left U-turn stop is designed to communicate that making a left U-turn is prohibited. This restriction helps ensure the safety and smooth flow of traffic, especially in areas where left U-turns may cause hazards or disrupt the movement of vehicles traveling along the road. When drivers encounter this sign, they must look for alternative routes or maneuvers to navigate, reinforcing adherence to traffic laws aimed at maintaining order on the roads.

The other options do not accurately interpret the meaning of the sign, as they suggest either permission for alternative turns or provide insufficient cautionary advice, contradicting the clear intent of prohibiting left U-turns.