What do two solid yellow lines mean on the road?

Two solid yellow lines indicate that passing is not allowed. This marking warns drivers that the road ahead does not permit crossing these lines under normal conditions, which is typically due to safety considerations such as limited visibility or hazardous conditions ahead. The presence of these lines serves to maintain safe driving practices by preventing drivers from attempting to pass vehicles in areas where it could be dangerous. Therefore, it is important for drivers to adhere to this rule to ensure the safety of all road users.

The other options might suggest conditions under which passing could be considered, but all of those scenarios are incorrect when solid yellow lines are present.