See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

**Analysis of C=C Bond Lengths** Bond length depends on bond order and hybridization. Higher bond order → shorter bond; greater s-character → shorter bond. **Identifying each compound:** - **I (Benzene):** Aromatic $sp^2$ C=C with resonance stabilization; bond order ≈ 1.5 - **II (Cyclohexene derivative):** Isolated $sp^2$ C=C; bond order = 2 - **III (Benzene):** Same as I; bond order ≈ 1.5 - **IV (Cyclohexane):** Single C-C bond; bond order = 1 **Ranking by bond length (longest to shortest):** $$\text{IV (C-C, order 1)} > \text{III & I (C=C aromatic, order 1.5)} > \text{II (C=C alkene, order 2)}$$ Since III and I are identical (both benzene with aromatic C=C), they have equal bond lengths. The decreasing order is: $$\boxed{\text{III} > \text{I} > \text{II} > \text{IV}}$$ **Why Option B is correct:** It correctly shows aromatic C=C bonds (III, I) as longer than isolated alkene C=C (II), which is longer than saturated C-C (IV). The fundamental principle: *conjugation/resonance reduces bond order, making bonds longer*.