Concept:An exothermic reaction releases heat energy, so we check which reaction types always do this.
Explanation:Neutralisation is always exothermic because acid-base reactions release heat, so statement I is correct.
Combustion is always exothermic because burning fuels or substances releases large amounts of heat and light, so statement III is correct.
Decomposition is not always exothermic. Many decomposition reactions, such as heating calcium carbonate, require heat and are endothermic. Others may release heat, but the process is not always exothermic, so statement II is not correct.
Therefore, the reactions that are always exothermic are I and III only.
Answer:B. I and III only