2. Sample Papers
  3. Railways
  4. General Science & Technology
  5. Pollution of Air and Water

Railways General Science & Technology Pollution of Air and Water Sample Paper Water Pollution Sample Test Paper-21

  • question_answer
    Biological oxygen demand of____ is the least.

    A)  Sewage

    B)  sea water

    C)  Pure water       

    D)  polluted water

    Correct Answer: C

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