Which agency is responsible for issuing health certificates for the transport of animals across borders?

The correct choice is B, the Animal and Plant Health Inspection Service (USDA-APHIS), because this agency plays a critical role in safeguarding animal health and regulating the movement of animals both domestically and internationally. USDA-APHIS is responsible for issuing health certificates that ensure that animals being transported meet specific health standards and are free from diseases that could be transmitted across borders. This is essential for maintaining public health as well as the health of livestock and wildlife populations.

The other agencies mentioned have distinct but different responsibilities. The Centers for Disease Control and Prevention (CDC) focuses more on public health initiatives and monitoring diseases that affect humans rather than directly managing animal health transport regulations. The Food and Agriculture Organization (FAO) provides international guidance and support related to food security and agricultural practices but does not issue health certificates for animal transport. The World Health Organization (WHO) primarily concerns itself with public health issues on a global scale, focusing on human health rather than animal transport regulations.