Question

2 fill in the blank 2 points a dead zone is defined as oxygen levels below choose your answer... ppm. previous

Explanation:

A dead zone in aquatic environments is defined as an area with dissolved oxygen levels below 2 - 3 ppm (though commonly, the threshold used in many definitions is 2 ppm, but among the given options, 3 is a recognized threshold for some definitions or contexts). The options are 3, 5, 1.5. The correct threshold for a dead zone (hypoxic zone) in terms of dissolved oxygen is typically below 2 - 3 ppm, so from the given options, 3 is the appropriate choice.

Answer:

3