Biological Oxygen Demand (BOD) is a standard criterion for
- (a) Measuring oxygen levels in blood
- (b) Computing oxygen levels in forest ecosystems
- (c) Pollution assay in aquatic ecosystems ✓ UPSC's answer
- (d) Assessing oxygen levels in high altitude regions
Why the answer is (c)
• Biological Oxygen Demand is the amount of dissolved oxygen that microbes consume while decomposing organic matter in a water sample over five days at 20 °C.
• A high BOD indicates heavy organic pollution (sewage, industrial effluent) that starves aquatic life of oxygen, so BOD is a standard measure of pollution in rivers and lakes — option (c).
• It is not used for blood (a), forests (b) or high-altitude air (d).
• Hence option (c).
Why the other options are wrong
- (a) Measuring oxygen levels in blood
- Blood oxygen is measured by oximetry, not BOD.
- (b) Computing oxygen levels in forest ecosystems
- BOD is a water-quality measure, not a forest one.
- (d) Assessing oxygen levels in high altitude regions
- BOD does not measure atmospheric oxygen.
Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2017, held on 18 June 2017. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.