What does a no entry sign look like?

Answer: B — red circle with a horizontal white bar

A no entry sign is characterized by a red circle with a horizontal white bar across its center. This design is universally recognized and indicates that vehicles are prohibited from entering a specific area, ensuring safety and compliance with traffic regulations. The distinctive shape and color scheme serve to attract the attention of drivers, reducing the likelihood of unauthorized entry into restricted zones, such as one-way streets or access-controlled areas. The other options present designs used for different traffic control purposes. For instance, a red triangle with a white border typically signifies warning signs, a yellow diamond with a black symbol usually indicates caution or advisory notices, and a blue square with a white arrow often directs traffic or provides information about allowed maneuvers. Each of these has its specific role in traffic regulation and does not convey the same prohibition as the no entry sign.