Exposure to which sound level for a short period can damage the eardrum?

Eutrophication can be observed in

Define $BOD$ (Biochemical Oxygen Demand).

Which of the following atmospheric pollutants causes general chlorosis,i.e.,destruction of chlorophyll?

Which one of the following is the heavy toxic metal present in waste water from industries?

If the concentration of $DDT$ in water is $0.003\, ppm$,what could be its concentration in small fish due to biomagnification (in $, ppm$)?