Which of the following is a human cause of wildfires?

Campsite fires are a significant human cause of wildfires because they often result from recreational activities where individuals gather for camping and cooking. If not properly controlled or extinguished, these fires can easily spread to the surrounding vegetation, especially in dry conditions or areas with abundant fuel sources.

On the other hand, spontaneous combustion refers to the natural heating of organic materials, which can ignite without an external spark. This phenomenon is not directly tied to human actions. Weather conditions, such as drought or high winds, can certainly exacerbate the spread of wildfires, but they are not human-caused factors. Similarly, earthquakes may lead to fires by damaging infrastructure or gas lines, but the earthquakes themselves are natural events, not human-induced. Therefore, among the choices given, campsite fires represent a clear example of human-caused wildfires, highlighting the importance of fire safety and prevention measures during outdoor activities.