Assertion A: Slow sand filters are more efficient in removal of bacteria than rapid sand filters.Reason R: The sand used in slow sand filters is finer than that in rapid sand filtersSelect your answer based on the coding system given below:

• A. Both A and R is true but R is not the correct explanation of A
• B. Both A and R is true and R is the correct explanation of A
• C. A is false but R is true
• D. A is true but R is false

Answer: (B)