Carbon-Carbon bond length in benzene is $.....$ $\mathring{A}$

Which position will be attacked most rapidly by the nitronium ion $(NO_2)^+$ when the compound undergoes nitration with $HNO_3 / H_2SO_4$?

Decide the correct order of reactivity of the following compounds towards electrophilic aromatic substitution (halogenation) with $(Cl_2 + AlCl_3)$:
$I$: Phenyl benzoate $(C_6H_5COOC_6H_5)$
$II$: Toluene $(C_6H_5CH_3)$
$III$: Ethylbenzene $(C_6H_5CH_2CH_3)$
$IV$: Benzene $(C_6H_6)$

The correct order of reactivity towards Electrophilic Substitution Reaction $(E.S.R.)$ for the following compounds is:
$(i)$ Toluene
(ii) $m$-Methoxytoluene
(iii) Benzaldehyde
(iv) $p$-Nitrobenzaldehyde

In pyrrole,the electron density is maximum on

The conversion of benzene to toluene is carried out by .........