As compared to rapid sand filters, slow sand filters give (i) Slower filtration rate (ii) Higher filtration rate (iii) Lesser efficiency in removal of bacteria (iv) Higher efficiency in removal of bacteria The correct answer is

• A. (i) and (iv)
• B. (ii) and (iii)
• C. (i) and (ii)
• D. (ii) and (iv)

Answer: (A)