Define BOD. What is its significance in an aquatic ecosystem?</h2></div>

Decomposition of organic wastes in water causes </h2></div>

Fish die in water bodies polluted by sewage due to</h2></div>

Which of the following problem occurs due to the use of nuclear energy?

What are the sources of water pollution? What steps could be taken to prevent water pollution?</h2></div>

<span>The hard mineral crust formed at or near the surface of soil is known as</span></h2></div>

Which of the following are main responsible for ozone depletion?</h2></div>

Mention any three human activities which are responsible for depletion of the ozone layer.</h2></div>