Which of the following is covered under P.C. § 451?

The correct answer is arson, as defined under Penal Code § 451. This section specifically addresses the act of willfully setting fire to or causing to be burned any structure, forest land, or property. Arson entails the intent to cause damage through fire, and it encompasses a range of acts from intentionally igniting materials to causing fires through reckless behavior that endangers life or property.

In contrast, the other options each pertain to different legal statutes. Resisting a Peace Officer involves actions taken to obstruct or hinder law enforcement in the execution of their duties and falls under a separate category of law. Trespassing concerns unlawful entry onto someone else's property without permission and is governed by different laws. Robbery involves taking property unlawfully from a person or immediate presence through force or intimidation, which is also addressed under different statutes.

Understanding the specific categories and definitions of these crimes is essential for clarity in law enforcement and legal studies, particularly regarding the application of California’s legal code.