Which of the following is an example of restricted visibility?

Restricted visibility refers to conditions in which the ability to see and identify vessels, land, or navigational aids is diminished. Fog is a prime example of such conditions, as it can significantly reduce the distance a person can see, affecting navigation and safety at sea. In fog, the limitations in visibility can lead to challenges in detecting other vessels, potential hazards, and navigating safely.

In contrast, sunshine, clear skies, and daylight all contribute to optimal visibility conditions where a navigator can see a significant distance and identify other vessels or navigational markers without obstruction. These conditions enhance safety and reduce the likelihood of collisions. Thus, fog distinctly represents a scenario of restricted visibility, making it the correct answer.