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 DO. concentration was 5 mg/l. The BOD of raw sewerage is

3.0 ml of raw sewage is diluted to 300 ml. The D.O. concentration of t

1.	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 DO. concentration was 5 mg/l. The BOD of raw sewerage is
A.	100 mg/l
B.	200 mg/l
C.	300 mg/l
D.	400 mg/l.
Answer» D. 400 mg/l.