A dead zone is an area … . a. that is undergoing secondary succession b. in terrestrial ecosystems where background extinction levels are causing a change in their normal flora and fauna c. on Earth with no living components and only non-livin

The correct answer is: **d. in lakes and oceans near the mouths of rivers where large areas are periodically depleted of their normal flora and fauna** Dead zones are areas in aquatic environments where the oxygen levels are very low (hypoxia), often due to nutrient runoff from land, leading to excessive algae growth (eutrophication). When the algae die, their decomposition consumes oxygen, making it difficult for marine life to survive.