Chlorobenzene ($\mathrm{C_6H_5Cl}$) is MUCH LESS reactive toward nucleophilic substitution than chloroethane. The main reason is

1. NCERT §6.7 (Haloarenes — substitution): the chlorine in chlorobenzene is significantly LESS reactive than in chloroalkanes for two reasons. 2. RESONANCE: the chlorine lone pair conjugates with the benzene $\pi$-system, giving the C-Cl bond PARTIAL DOUBLE-BOND character. Double bonds are stronger and harder to break. 3. The carbon bonded to Cl in chlorobenzene is $sp^2$ hybridised (in the ring), while in chloroethane it's $sp^3$. $sp^2$ C-X bonds are SHORTER and STRONGER than $sp^3$ ones — another factor making chlorobenzene unreactive. 4. Net: nucleophilic substitution on chlorobenzene requires harsh conditions (e.g. NaOH at $623\,\text{K}$ and 300 atm — the Dow process for phenol). 5. Option A confuses the cause (electronegativity isn't the dominant factor). Option C and D are physically wrong (chlorobenzene is liquid, similarly polar to chloroethane). _Source: NCERT Class 12 Chemistry Part 2, Ch 6, §6.7 (Haloarenes — low reactivity, resonance argument), p. 18–19._