Question

what do we use to prevent the mixture of potable and non - potable water?
cross - contamination
air gap
backflow
cross - connection

Explanation:

An air - gap is a physical separation between the outlet of a potable water supply and the potential source of contamination (non - potable water). It prevents backflow and cross - connection, thus avoiding cross - contamination. Cross - contamination is the result of improper separation, backflow is the reverse flow of water which can cause mixing, and cross - connection is an actual connection between potable and non - potable water systems that should be avoided.

Answer:

B. Air gap