Outbreaks of giardiasis have occurred in numerous places where drinking water treatment plants did not provide:

Outbreaks of giardiasis have occurred in numerous places where drinking water treatment plants did not provide proper filtration and purification of fecally contaminated water supplied to the public. Garidia is a protist that lives in the intestines of warm blooded animals and is highly resistant to chlorination due to the presence of cysts.

Your answer is water because there is combined mass of water found on, under, and over the surface of a planet. your answer is water.