Water pollution and eutrophication – UGC NET Question

Statement D is the only wrong statement because eutrophication usually leads to algal blooms that can deplete dissolved oxygen and harm aquatic life rather than benefit it. Statements A, B and C correctly explain the process of eutrophication, the nature of point sources and examples of non-point sources such as agricultural runoff. Thus, identifying D only as the wrong statement matches the scientific understanding of water pollution and eutrophication.

Option A:
Option A is incorrect because it treats statement A as wrong, whereas A correctly defines eutrophication as nutrient enrichment causing excessive algal growth in water bodies. This phenomenon is widely recognised in limnology and environmental science. Misclassifying a correct definition as wrong makes this option invalid.

Option B:
Option B is correct because it pinpoints D as the single incorrect statement. Eutrophication tends to reduce oxygen levels through decomposition of algal biomass and can lead to fish kills and ecosystem degradation. Since A, B and C are accurate descriptions of relevant concepts, focusing on D only as wrong is logically consistent with the question.

Option C:
Option C is incorrect because it assumes both A and D are wrong. While D is indeed wrong, A is correct and supported by numerous environmental case studies on lakes and reservoirs. Including a correct statement in the set of wrong statements makes the combination unacceptable.

Option D:
Option D is incorrect because it groups C and D together as wrong statements. Although D is wrong, C is correct in identifying agricultural runoff and urban stormwater as typical non-point sources. Treating C as wrong contradicts standard classifications used in pollution control.