When is it illegal to pass another vehicle?

Answer: B — When there is a solid yellow line on your side of the roadway

Passing is illegal when there is a solid yellow line on your side of the roadway because this line indicates that it is unsafe to overtake another vehicle. Solid yellow lines are used to separate lanes of traffic that are moving in opposite directions, and their presence signifies that visibility is likely limited or that conditions are not safe for passing. In contrast, while a double yellow line also prohibits passing, it does so for both sides of the roadway, indicating a more stringent restriction. The other options do not directly relate to a clear violation of passing rules; in some cases, passing may still be permissible depending on the specific circumstances, such as at a traffic signal or when speed limits change, provided that it is safe to do so.