Final answer:
Entering a locked trunk of an unlocked vehicle with the intent to steal is considered burglary, as it involves breaking into a secured space unlawfully.
Step-by-step explanation:
Entering the locked trunk of an unlocked vehicle to commit a theft is an example of burglary. Although the vehicle itself is not locked, the trunk is a secured space, and the action of breaking into it with the intent to commit a theft constitutes burglary. This is covered under the definition where burglary is considered as entering a building or other premises with the intent to commit a crime, especially theft. Therefore, the correct answer to the question is D) burglary.