Which pollutant poses a threat to the $Taj$ $Mahal$?

$NO_2$ and $O_3$ react with unburnt hydrocarbons in polluted air to form .....

The greenhouse effect is caused by which of the following?

Given below are two statements :
Statement $I :$ The $pH$ of rain water is normally $\sim 5.6$.
Statement $II :$ If the $pH$ of rain water drops below $5.6,$ it is called acid rain.
In the light of the above statements,choose the correct answer from the options given below:

The compound that is $NOT$ a common component of photochemical smog is

Pollution can be controlled by