Identify the correct statements from the following

I. Photochemical smog has high concentration of oxidising agents.

II. $\mathrm{NO}_2$ is present in classical smog.

III. Higher concentration of $\mathrm{SO}_2$ in air can cause stiffness of flower buds.

IV. pH of rain water is approximately 7.5 .

Consider the given sequence of reactions,

$$ \mathrm{C}_2 \mathrm{H}_6+\frac{3}{2} \mathrm{O}_2 \xrightarrow[\Delta]{(\mathrm{CH}, \mathrm{COO})_2 \mathrm{Mn}} X \xrightarrow{\mathrm{Na}} Y $$

Electrolysis of aqueous solution of $Y$ gives gases $P$ and $Q$ at anode. $P$ and $Q$ are respectively

When sodium fusion extract of an organic compound is boiled with iron (II)sulphate solution followed by addition of concentrated $\mathrm{H}_2 \mathrm{SO}_4$, gives prussian blue colour. This confirms the presence of the element

Which of the following is an example of electrophilic substitution reaction?