What does a solid yellow line indicate?

A solid yellow line is a crucial road marking that indicates that passing or overtaking other vehicles in that lane is not allowed. This is typically found on roads where visibility is limited, such as curves or hills, where any attempt to pass could lead to dangerous situations for both the driver making the maneuver and oncoming traffic. The solid line serves as a clear warning to drivers that they must remain in their lane and cannot cross over to pass another vehicle, promoting safety on the road. This is why the answer provided is correct; it emphasizes the importance of adhering to traffic rules aimed at reducing accidents and maintaining order on the roadways.

Other options might suggest that passing is permitted or indicate the presence of bicycle lanes or speed zone changes, but these do not apply in contexts where solid yellow lines are used.