Aerobic lagoons contain oxygen that allows air-breathing organisms to exist, so these are typically shallow lagoons up to 5 feet deep (the third choice).
Anaerobic lagoons are made to not contain any oxygen, and since oxygen can diffuse in from the surface, they are made as deep as possible, such as from 6 to 30 feet deep (the first choice). Organisms that survive in an absence of air are grown in these lagoons.
Finally, facultative lagoons contain both aerobic and anaerobic zones, so their depth is in the middle as well (4 to 8 feet deep, the second choice).
