Biological Oxygen Demand (BOD) is a standard criterion for

Biological Oxygen Demand (BOD) is the standard criterion for pollution assay in aquatic ecosystems because it measures the amount of dissolved oxygen required by aerobic microorganisms to decompose organic matter, where higher BOD indicates higher levels of organic pollution. While option (a) might tempt those thinking of biological systems, oxygen levels in blood are measured through clinical methods like pulse oximetry, whereas BOD is strictly an environmental metric for water quality. The core concept being tested is the relationship between microbial decomposition of waste and the depletion of dissolved oxygen in water bodies.