The dissolved oxygen level in natural unpolluted waters at normal temperature is found to be of the order of
A. 1 mg/litre
B. 10 mg/litre
C. 100 mg/litre
D. 1000 mg/litre
Answer:B
The dissolved oxygen level in natural unpolluted waters at normal temperature is found to be of the order of
A. 1 mg/litre B. 10 mg/litre C. 100 mg/litre D. 1000 mg/litre