Chemical reactions that release energy

a. will not occur

b. need catalysts to occur

c. will always explode

d. often occuer spontaneously

The answer is D. The reaction always towards engergy releasing and entropy increasing. So the reactions that release energy can occur spontaneously. For B, catalysts can only increase the reaction speed. It can not trigger one specific reaction. For C, many mild reaction can release energy, like NaOH + HCl.