What mean(s) that passing is not allowed in either direction?

Answer: D — Two solid yellow lines

In Washington State, two solid yellow lines means that passing is not allowed in either direction. These double yellow lines indicate that it is unsafe to pass, as they are typically present in areas with limited visibility or other hazards where passing could be dangerous. It is crucial for drivers to pay attention to these road markings and refrain from passing when they encounter two solid yellow lines to ensure the safety of everyone on the road. Broken white lines (Option A), single broken yellow lines (Option C), and one solid yellow line (Option B) all allow for passing under certain conditions, unlike two solid yellow lines which prohibit passing in both directions.