Encouraging your sick friends to hang out with you does not help prevent the spread of infectious diseases, in fact, it could potentially contribute to the spread of the disease. The other options listed - washing hands, practicing food safety, and up-to-date immunizations - all help to prevent the spread of infectious diseases.
what is the answer
Washing hands, practicing food safety, and up-to-date immunizations help prevent the spread of infectious diseases. Encouraging sick friends to hang out with you does not help prevent the spread of infectious diseases.
