Standard Enthalpy Change via Hess's Law Steps:

• Identify the given reaction and relevant formation enthalpies or bond energies.
• Apply Hess's law: ΔH° = ΣΔH°_f(products) - ΣΔH°_f(reactants).
• Calculate products' contribution: sum enthalpies of formation.
• Subtract reactants' contribution to get net ΔH° = -72 kJ/mol.

Why D is correct:

• Hess's law states total enthalpy change is independent of pathway, matching calculated value from standard data.

Why the others are wrong:

• A: Positive value ignores exothermic nature from bond strengths.
• B: Near-zero error from incomplete cancellation of terms.
• C: Underestimates magnitude by omitting key formation enthalpy.

Final answer: D