If the diameter of a sewer is 150 mm, the gradient required for generating self cleansing velocity, is

A. Fit for discharge into any open drain B. Foul and contains dissolved and suspended solids C. As good as that from a complete treatment D. None of these

A. 0°C B. 15°C C. 20°C D. 25°C

A. 1 in 5 B. 1 in 10 C. 1 in 15 D. 1 in 20

A. Without entry ladders B. Without manhole covers C. With depths more than 3.5 m D. Having drains at different levels