What action is prohibited when passing another vehicle?

Passing when there is a solid line is prohibited because solid lines indicate that it is unsafe to overtake and pass another vehicle in that specific area. A solid line typically signifies that visibility is limited or that conditions are not suitable for passing, which helps maintain safety on the road. When a driver observes a solid line, it serves as a clear warning that passing could lead to dangerous situations. It is crucial for drivers to adhere to these markings to ensure their own safety and the safety of others on the road.

In contrast, options concerning passing on the left, passing during daylight hours, or passing on the right are not necessarily prohibited under normal circumstances. Each of these actions can be safe and legal depending on the relevant road laws and traffic conditions, provided that they do not violate other specific regulations such as those involving solid lines.