If n is the rugosity coefficient, r is the hydraulic depth, s is the bed slope of sewer, the velocity of flow in m/sec may be obtained by the formula $${\text{V}} = \frac{1}{{\text{n}}}{{\text{r}}^{\frac{2}{3}}}{{\text{s}}^{\frac{1}{2}}}$$   evolved by

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