Explain why only one mono-substitution product is possible in benzene. Provide examples of its structure and name.

(N/A) Benzene $(C_6H_6)$ consists of a planar hexagonal ring of $6$ carbon atoms,each attached to one hydrogen atom.
All $6$ hydrogen atoms in benzene are equivalent due to the resonance-stabilized structure,meaning they occupy identical chemical environments.
Therefore,the replacement of any one of these $6$ hydrogen atoms by a substituent group $(A)$ results in the formation of only one unique mono-substituted benzene product.
Examples include:
$1$. Methylbenzene (Toluene): $C_6H_5CH_3$
$2$. Nitrobenzene: $C_6H_5NO_2$
$3$. Chlorobenzene: $C_6H_5Cl$
$4$. Bromobenzene: $C_6H_5Br$
$5$. Ethylbenzene: $C_6H_5CH_2CH_3$
$6$. Hydroxybenzene (Phenol): $C_6H_5OH$