Final answer:
The Boston Police Department is the oldest policing authority in the United States among the provided options. The FBI and DEA are federal agencies that deal with specific federal law enforcement responsibilities, while local departments like Boston's have a broad scope of community policing.
Step-by-step explanation:
The oldest policing authority in the United States is the Boston Police Department (D). Police forces are responsible for enforcing laws and maintaining public order, and they can exist at federal, state, or community levels. Policing in the United States is not unified at the national level; instead, various federal agencies such as the Federal Bureau of Investigation (FBI), the Drug Enforcement Administration (DEA), and the Department of Homeland Security (DHS) each have specific roles. Federal officers have jurisdiction only in matters specified by federal law, often focusing on more narrow areas of expertise.
The FBI serves as the chief federal law enforcement agency within the United States, although its powers are constrained by constitutional protections like the Fourth Amendment. Unlike local or municipal police forces that have a broader scope of patrol and community involvement, federal agencies, including the DEA, typically focus on matters relating to national security and federal law.