What is the primary purpose of official traffic-control devices?

The primary purpose of official traffic-control devices is to regulate, warn, and guide traffic. These devices are essential for maintaining order on roadways and ensuring the safety of all road users, including drivers, pedestrians, and cyclists. Traffic-control devices include stop signs, traffic signals, road markings, and warning signs, all of which facilitate safe navigation and help prevent accidents. By clearly conveying information about traffic laws, hazards, and directions, they enable drivers to make informed decisions while driving.

The other options do not align with the fundamental function of traffic-control devices. While drivers may appreciate knowing the location of landmarks for navigation, that is not the primary role of these devices. Additionally, providing entertainment is not their purpose, as the focus is specifically on safety and the regulation of traffic. Finally, displaying advertisements does not fall under the category of official traffic-control devices, which are instituted by government authorities for maintaining traffic order. Thus, the correct choice emphasizes the critical role these devices play in promoting safe and effective traffic management.