What does a red line through a red circle indicate?

A red line through a red circle is a universal symbol indicating a prohibition. This sign typically communicates that a specific action or behavior is not allowed. For instance, it may signify that a turn is prohibited, or that entering a certain area is banned. Understanding this sign is crucial for compliance with traffic laws and for ensuring the safety of all road users.

In this context, the other options do not align with the meaning of this traffic sign. Stopping, slowing down, or proceeding with caution are actions that suggest permission or a need for vigilance rather than an outright prohibition. Thus, option B accurately reflects the implications of the red line through the red circle, emphasizing the necessity to refrain from the indicated action.