Acrolein $(X)$ is one of the chemicals formed when $O_3$ and $NO_2$ react with unburnt hydrocarbons present in the polluted air. The structure of '$X$' is

Leakage of which gas was responsible for the Bhopal tragedy in $1984$?

Give the details of the different layers of the atmosphere and briefly describe the substances present in them.

Which one of the following depletes the ozone layer?

Some gases are responsible for the heating of the atmosphere (greenhouse effect). Identify from the following the gaseous species which does not cause it.

Given below are two statements :
Statement $I$ : If $BOD$ is $4\,ppm$ and dissolved oxygen is $8\,ppm$,then it is a good quality water.
Statement $II$ : If the concentration of zinc and nitrate salts are $5\,ppm$ each,then it can be a good quality water.
In the light of the above statements,choose the most appropriate answer from the options given below :