3.0 ml of raw sewage is diluted to 300 ml. The D.O. concentration of the diluted sample at the beginning of the test was 8 mg/l. After 5 day-incubation at 20°C, the D.O. concentration was 5 mg/l. The BOD of raw sewerage 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