Which of the following statements about smog is correct?

Observe the following statements:
Statement-$I$: The carbon-containing components of photochemical smog are acrolein,methanal,and $PAN$.
Statement-$II$: The number of greenhouse gases in the list given below is $5$: $CH_4, CO_2, NO, H_2O_{(l)}, H_2O_{(g)}, O_2, O_3$.
The correct answer is:

In an agricultural field,which among the following is the highest producer of methane?

The presence of ozone in the troposphere:

Match $List-I$ with $List-II$:

$List-I$ (Pollutant)	$List-II$ (Source)
$A$. Microorganisms	$I$. Strip mining
$B$. Plant nutrients	$II$. Domestic sewage
$C$. Toxic heavy metals	$III$. Chemical fertilizer
$D$. Sediment	$IV$. Chemical factory

Choose the correct answer from the options given below:

How is nitrogen oxide formed in the atmosphere,and why is an excessive amount of nitrogen oxide harmful?