Biology · MICROBES IN HUMAN WELFARE

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Primary treatment of sewage mainly involves the physical removal of particles—large and small—from the sewage through filtration and sedimentation. Reason (R): Secondary treatment of sewage relies heavily on the growth of aerobic microbes into flocs that consume organic matter and reduce BOD. In the light of the above statements, choose the correct answer from the options given below:

1. A
   Both (A) and (R) are true and (R) is the correct explanation of (A).
2. B
   Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
3. C
   Statement (A) is true but (R) is false.
4. D
   Statement (A) is false but (R) is true.