What agency is responsible for inspecting dogs and cats at ports of entry?

The agency responsible for inspecting dogs and cats at ports of entry is the Department of Homeland Security - Customs and Border Protection. This agency plays a critical role in protecting the nation's borders and ensures that animals entering the country do not pose a health risk to public safety or the environment. They conduct inspections at ports of entry to ensure compliance with import regulations related to the health and safety of animals.

The other choices, while related to animal health, do not have the primary responsibility for these inspections at ports. The USDA encompasses various divisions, including APHIS, but it is the Customs and Border Protection that performs direct inspections at the borders. APHIS focuses on protecting animal health domestically and abroad but works in conjunction with Customs and Border Protection rather than performing the inspections themselves at the ports. Therefore, the choice of the Department of Homeland Security - Customs and Border Protection is accurate in this context.