Phoresy is a smaller creatures that uses larger creatures to move large distances. Altruism is the behavior where an animal puts another's needs before their own. Commensalism is a beneficial relationship for one party and nutral to the other. Mutualism is beneficial to both parties.
The answer is Altruism.
All of the above.
They can be prevented, especially Polio.
Smallpox is common in children, but potentially deadly in baby's.
Influenza is the flu.
