Which of the following would be considered the "portal of exit" for influenza A?

The "portal of exit" in the context of infectious diseases refers to the path through which a pathogen leaves its host to potentially infect another individual. For influenza A, respiratory secretions are the main means by which the virus is transmitted. When an infected person sneezes or coughs, respiratory droplets containing the virus are expelled into the air. This action exemplifies how the influenza virus exits the body of an infected individual, making sneezing or coughing the primary portal of exit for the virus.

While contact with contaminated surfaces and inhalation of infected air are important aspects of transmission, they do not describe how the virus exits the host—rather, they represent pathways of how the virus can subsequently infect others. Consumption of contaminated food is primarily associated with gastrointestinal viruses and does not pertain to the respiratory transmission crucial for influenza A. Thus, sneezing or coughing distinctly illustrates the direct mechanism through which influenza A leaves the infected person, highlighting its role as the correct answer.