Which of the following is a typical cause of wildfires in California?

Human activity is a typical cause of wildfires in California due to a variety of factors. People are often responsible for igniting fires through activities such as campfires left unattended, discarded cigarettes, burning debris, and sparks from electrical equipment or vehicles. In many cases, the growing population and increasing urban development in fire-prone areas result in more interactions between human activities and natural landscapes, leading to a higher likelihood of wildfires.

In contrast, while excessive rainfall may encourage vegetation growth, it does not directly cause wildfires; instead, it can be seen to contribute to later fire risks when dry conditions return. Volcanic activity, although capable of starting fires, is a rare occurrence compared to the more commonplace human-induced factors. Pollution levels, while a significant environmental concern, are not a direct cause of wildfires but may affect air quality during fire events. Thus, human activity stands out as the predominant cause of wildfires in the state.