How is excessive content of $CO_{2}$ responsible for global warming?

Mention two side effects caused by acid rain.

Identify the correct statements from the following:
$a$) $BOD$ value of clean water is less than $5 \ ppm$
$b$) Oxidation of ethene in the presence of $Pd^{2+}$ catalyst in aqueous medium gives acetic acid
$c$) Photochemical smog causes damage to plant life
$d$) Reducing smog is a mixture of smoke,fog and $SO_2$

The depletion of ozone in the atmosphere by chlorofluorocarbons [$CCl_2F_2$] is a ...... statement.

Which of the following is a secondary pollutant?

Have you ever observed any water pollution in your area? What measures would you suggest to control it?