When is passing another vehicle prohibited?

Answer: B — When the traffic situation is unclear.

Passing another vehicle is prohibited when the traffic situation is unclear because this condition can pose significant safety risks for both the driver attempting to pass and other road users. When the traffic situation is unclear, it implies a lack of certainty regarding the movements of other vehicles, pedestrians, or potential obstacles. Attempting to pass under such circumstances can lead to accidents if another vehicle suddenly changes lanes, turns, or if a pedestrian unexpectedly steps into the roadway. In contrast, while passing should generally be approached with caution regardless of the circumstances, there are specific guidelines around visibility, traffic lights, and road width. Limited visibility may certainly make passing dangerous, as would narrow roads, but these conditions alone may not always outright prohibit passing. However, an unclear traffic situation establishes a context where the safety of the maneuver is compromised, making it most critical to avoid passing in those circumstances.