What is illegal when passing another vehicle?

When passing another vehicle, there are specific rules in place to ensure the safety of all road users. Crossing a solid line is illegal because solid lines indicate that passing is not permitted due to potential hazards, such as limited visibility or a high likelihood of encountering oncoming traffic. Exceeding the speed limit is also illegal as it increases the risk of accidents and decreases the driver's ability to react in emergencies. Additionally, passing on a curve is dangerous and illegal because curves limit visibility; drivers may not have adequate sight of oncoming vehicles, which increases the risk of collision. Given these considerations, all the actions mentioned are illegal when attempting to pass another vehicle, making the comprehensive answer correct.