This white sign means you should not pass other vehicles:

Until after you pass the sign.
Unless it seems safe to do so.
For any reason.
The Correct Answer and Explanation is :
The correct answer is: For any reason.
Explanation:
The “Do Not Pass” sign is a regulatory road sign that prohibits drivers from passing other vehicles for any reason while traveling in that area. These signs are typically placed in locations where it would be unsafe or illegal to overtake another vehicle. For instance, this could include areas with limited visibility, sharp curves, hills, or near intersections.
Why Passing is Prohibited:
- Limited Visibility: If the road ahead is not clearly visible due to hills, curves, or other obstructions, passing could lead to a head-on collision with oncoming traffic.
- Hazardous Conditions: Roads with narrow lanes, bridges, or areas under construction often have “Do Not Pass” zones to prevent accidents.
- Safety of Pedestrians and Cyclists: On roads shared with pedestrians, bicycles, or slow-moving vehicles, passing could endanger vulnerable road users.
Legal Implications:
Failing to obey a “Do Not Pass” sign is considered a traffic violation in most states. Violations can result in fines, points on your driving record, and increased insurance premiums. Repeated offenses might lead to license suspension.
Safe Driving Practices:
- Always observe road signs and comply with their instructions.
- Stay alert for additional warning signs indicating the end of the “No Passing” zone.
- If you’re in a situation where passing seems possible but the sign prohibits it, resist the temptation. Safety regulations are based on studies of road conditions and traffic patterns.
In summary, the “Do Not Pass” sign means no passing for any reason. Adhering to this rule ensures your safety and that of others on the road.