Ncert Exercises & Solutions

Given below are two statements:

Assertion (A):	If the BOD level of water in a reservoir is less than 5 ppm it is highly polluted.
Reason (R):	High biological oxygen demand means the low activity of bacteria in water.

1.	Both (A) and (R) are true and (R) is the correct explanation of (A).
2.	Both (A) and (R) are true but (R) is not the correct explanation of (A).
3.	(A) is true but (R) is false.
4.	Both (A) and (R) are false.