$A$ hydrocarbon does not decolorize alkaline $KMnO_4$ solution and does not give a precipitate with ammoniacal silver nitrate. This hydrocarbon is .......

Which of the following statements are correct?
$I$. In nitrating mixture,nitric acid participates as an acid.
$II$. $\sigma$-complex is the intermediate substance in electrophilic substitution of benzene.
$III$. Benzene on Friedel-Crafts alkylation with $n$-propyl chloride gives isopropyl benzene.

Calculate the sum of $\alpha$-hydrogen atoms in the given structures $(i)$ and $(ii)$:
$(i)$ $1,3$-dimethylbenzene
(ii) $1,3$-diethylbenzene
Sum $= (i) + (ii) = ?$

The electrophilic aromatic substitution proceeds through a

Which of the following compounds upon oxidation gives isophthalic acid?

Assertion : Tropylium cation is aromatic in nature.
Reason : The only property that determines its aromatic behaviour is its planar structure.