755. If the depletion of oxygen is found to be 2.5 mg/litre after incubating 2.5 ml of sewage diluted to 250 ml for 5 days at 20°C, B.O.D. of the sewage is_________________?

A. 50 mg/l
B. 100 mg/l
C. 150 mg/l
D. 250 mg/l
✅ The correct answer is option D.

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