What actions should be taken when driving in foggy conditions?

Using low-beam headlights and reducing speed is the most appropriate action to take when driving in foggy conditions. Low-beam headlights are effective in fog because they provide illumination closer to the road and don't reflect as much light back from the fog or mist, which can happen with high-beam headlights. This reduces glare and allows the driver to see the road and other vehicles more clearly.

Additionally, reducing speed is crucial in foggy conditions. Reduced visibility can make it harder to see obstacles, road signs, and other vehicles, so driving more slowly allows for better reaction times and increases safety. In fog, maintaining a safe distance from other vehicles becomes even more important, along with being prepared to stop if needed.

In contrast, the other options involve actions that would create additional hazards. For instance, using high-beam headlights can create dangerous glare, and increasing speed reduces your ability to react to unexpected conditions. Turning off headlights is unsafe as it significantly decreases visibility, and following closely behind other vehicles can lead to accidents if those vehicles suddenly slow down or stop, as you may not have enough time to react.