Question:
Water samples with BOD values of $4 \mathrm{ppm}$ and $18 \mathrm{ppm}$, respectively, are :
Correct Option: , 2
Solution:
Clean water would have BOD value $<5 \mathrm{ppm}$ whereas highly polluted water could have BOD value $\geq 17$ $\mathrm{ppm}$.