Question

The minimum dissolved oxygen required in water to save the aquatic life is ............

• A. 1 ppm
• B. 2 ppm
• C. 4 ppm
• D. 8 ppm

Hint:

Maintaining DO above 4 ppm is critical for the survival of aquatic organisms. Low DO levels are a key indicator of water pollution.

Answer 1

The Correct Option is C

Dissolved oxygen (DO) is essential for the survival of aquatic organisms. A certain minimum concentration of DO must be maintained in natural water bodies to support healthy aquatic life.
The generally accepted threshold for sustaining most forms of aquatic life is 4 ppm (parts per million). Below this level, oxygen becomes insufficient for many species, especially fish, leading to stress or death.
Therefore, the correct minimum value of DO to preserve aquatic life is 4 ppm. \[ \text{Minimum DO for aquatic life} \geq 4~\text{ppm} \]