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Environmental Issues — BIOLOGY STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceBIOLOGYEnvironmental Issues1 Mark
MCQ
Fishes die by sewage because:
  • ✓
    Of its bad smell.
  • B
    It replaces food material of fishes.
  • C
    It increases oxygen competition among fishes.
  • D
    $\mathrm{CO}_2$​ is mixed in large amount in water.
✓

Answer

Correct option: A.
Of its bad smell.
Sewage discharge in water bodies leads to organic loading or occurrence of excess organic matter inside water body.
Its putrefaction decreases dissolved oxygen leading to competition for oxygen among fishes. Also blue green algae bloom and increase in number and release toxins. Both toxicity and decreased oxygen level kill aquatic animals, like fishes.

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