Hello!
Gastroenteritis is another word for the Stomach Flu. It's an intestinal infection spread through either contact with an infected person or infected food.
This being said, if someone does not wash their hands properly or enough they are more likely to contract this infection, because they are not actively killing off those germs as frequently as they should be.
So to sum it up the answer to this is A. Not washing hands well enough.
Hope this helps answer your question!
