Which of the following is not an endothermic reaction ? (a) CaCO3→ CaO + CO2 (b) 2H2O → 2H2 + O2 (c) 6CO2 + 6H2O → C6H12O6 + 6O2 (d) C6H12O6 + 6O2→ 6CO2 + 6H2O

Option (d) is the answer. This is responsible for the respiration reaction in which glucose burns in oxygen to produce heat energy and thus an exothermic reaction