What does a solid white line indicate on a road?

Answer: B — The right edge of the traffic lane

A solid white line on a road is used to indicate the right edge of the traffic lane. It helps guide drivers by marking the boundary of the roadway, ensuring that vehicles stay within their designated lanes. The presence of a solid white line signifies that crossing it is discouraged, particularly during high traffic or in conditions where it may be unsafe to do so. This is crucial for maintaining orderly traffic flow and enhancing safety on the road. The other options provide different features of road marking that do not align with the meaning of a solid white line. Understanding this distinction can help drivers make better decisions and understand road signage more effectively.