Which of the following actions falls under the definition of "arson"?

The definition of "arson" specifically involves the willful and malicious setting of a fire to property. This means that for an act to be classified as arson, there must be intent to cause damage through the act of fire-setting. Option B clearly falls under this definition as it specifies that the fire is set voluntarily, indicating intent to ignite a structure purposely, which aligns with the criminal implications of arson.

In contrast, accidentally burning a building does not fit the criteria of arson since there is no intent to cause damage. Similarly, while using fireworks that cause property damage may result in unintended consequences, it doesn't necessarily connote the willful act of starting a fire as categorized in arson laws. Burning yard waste is often permissible and regulated under certain conditions, and typically wouldn’t be classified as arson unless it can be proven that it was done recklessly or in violation of specific regulations leading to endangerment of property.

Thus, the clear and intentional nature of option B is what categorizes it as arson within California Penal Codes.