- The BOD of industrial sewage can be calculated using the population equivalent, where the BOD value per person is typically around 0.08 kg/day.
- Therefore, for 6000 persons, the BOD will be \( 6000 \times 0.08 = 480 \) kg/day.
Conclusion: The BOD of industrial sewage is 480 kg/day, as given by option (A).