When is passing not allowed on either side of a road?

Answer: B — When both sides have solid yellow lines

Passing is not allowed on either side of a road when both sides have solid yellow lines. Solid yellow lines indicate that passing traffic is prohibited because it generally signifies that the road is narrow, there are potential hazards, or it is unsafe to overtake slower vehicles. This is a crucial safety measure to prevent accidents that can occur from attempting to pass when visibility is limited or when oncoming traffic is present. Other situations, such as the presence of bicycles or cautionary road signs, may suggest exercising caution but do not universally prohibit passing. Dashed yellow lines indicate that passing is allowed with caution, and therefore do not apply in this context. Understanding the meaning of line markings is vital for safe driving and adhering to traffic laws.