Polluted water bodies have:

Correct option is B

Correct Answer: (b)
Explanation:
Polluted, nutrient-rich water bodies commonly show abundant growth of green algal forms such as Spirogyra (filamentous green algae) and unicellular green algae like Chlamydomonas which proliferate under eutrophic conditions.
Information Booster:
-Eutrophication (high nutrients) favors rapid growth of green algae and cyanobacteria.
-Spirogyra forms green scum and mats in stagnant, polluted water.
-Chlamydomonas is a common unicellular green alga in freshwater.
-Presence of such blooms reduces water quality and oxygen availability.
-Identification helps indicate organic pollution and nutrient enrichment.
Additional Information (Incorrect Options):
(a)/(d) mix cyanobacteria and green algae — while possible, the classic indicators in many polluted stagnant waters are Spirogyra + Chlamydomonas.
(c) is same taxa as (b) but ordering differs; (b) is the standard pair listed in source.