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Assertion (A): If BOD level of water in a reservoir is less than 5 ppm it is highly polluted. 
Reason (R): High biological oxygen demand means low activity of bacteria in water. 
(i) Both A and R are correct, and R is the correct explanation of A. 
(ii) Both A and R are correct, but R is not the correct explanation of A. 
(iii) Both A and R are not correct. (iv) A is not correct but R is correct.

0 2 Views | Posted 4 months ago
Asked by Shiksha User

  • 1 Answer

  • A

    Answered by

    alok kumar singh | Contributor-Level 10

    4 months ago

    This is a  Assertion Type Questions as classified in NCERT Exemplar

    Option (iii)

     i.e.,   Both A and R are not correct since the amount of oxygen required by bacteria to breakdown the organic matter present in a certain volume of a sample of water, is called BOD i.e., Biochemical Oxygen Demand. If the BOD of the water is < 5 ppm then it is clean but if it increases then the water pollution increases.

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