Which government agency is primarily assigned to enforce land transportation regulations?

The Land Transportation Office (LTO) is the primary government agency responsible for enforcing land transportation regulations in the Philippines. Its core functions include the registration of motor vehicles, issuance of driver's licenses, and regulation of land transport services in the country. The LTO ensures compliance with various laws and policies related to land transportation, which helps maintain order and safety on the roads.

While the Land Transportation Franchising and Regulatory Board, Metro Manila Development Authority, and Department of Transportation also play roles in transportation regulation and management, they have different specific mandates. The Franchising and Regulatory Board focuses on the franchising of public transport services, the Metro Manila Development Authority primarily addresses metropolitan development and traffic management in Metro Manila, and the Department of Transportation oversees all transportation modalities, including land, air, and sea. Therefore, the LTO is distinctly tasked with the enforcement of regulations specifically pertaining to land transportation, making it the correct answer.