What does a single solid white line indicate about crossing?

Answer: B — Legal to cross but not recommended

A single solid white line indicates that while it is legal to cross, it is not recommended. This marking is typically used to separate lanes of traffic moving in the same direction. It serves as a cautionary measure, suggesting that changing lanes is generally discouraged due to potential hazards, such as reduced visibility or higher traffic density. While drivers have the legal right to cross this line if necessary, they should do so with caution and only when it is safe. The emphasis is on exercising good judgment and being aware of the traffic conditions when considering a lane change.