Final answer:
The National Institutes of Health (NIH) is responsible for enforcing the Public Health Service Policy on Humane Care and Use of Laboratory Animals.
Step-by-step explanation:
The agency responsible for enforcing the Public Health Service Policy on Humane Care and Use of Laboratory Animals is the National Institutes of Health (NIH). The NIH is a governmental agency that is part of the United States Department of Health and Human Services. They have developed strict regulations and guidelines, including the document called the "Guide for the Care and Use of Laboratory Animals", which sets standards for the housing, care, and treatment of animals used in research.