Biochemical Oxygen Demand (BOD) in a river water</h2></div>

<span class="katex"><span class="katex-html" aria-hidden="true"><span class…

The ozone layer  'ozonosphere' occurs in</h2></div>

What is Global Warming? Write their main five reasons.</h2></div>

Identify the harmful radiations emitted by the sun.</h2></div>

The gas that usually causes explosion in coal mines is</h2></div>

<span>Deforestation refers to</span><br> </h2></div>

Desertification is a type of</h2></div>