Provide the full forms of the following abbreviations:
$(i)$ $GAIL$
$(ii)$ $BOD$

The phenomenon in which nutrient enrichment of a water body supports a dense growth of one or many organisms but decreases the species diversity is called:

Assertion : Water pollutants are measured by $BOD$.
Reason : If $BOD$ is more,the water is polluted.

Disadvantages of chemical agents are:
$I.$ Chemicals are toxic and harmful to human beings and animals.
$II.$ Chemicals pollute the environment and plants.
$III.$ Weedicides used to remove weeds also pollute the soil.
Choose the correct option.

Foul smell in the water of tanks,ponds,etc.,is due to:

What is the intensity of sound in normal conversation?