What two terms are used to describe the enthalpy changes for the reactions?

Exothermic and endothermic

Explanation:

Enthalpy change of a reaction refers to the energy change between the reactants and the products. it is given by:

Enthalpy change = Energy of products - energy of reactants

Exothermic reactions are reactions that release heat energy to the surroundings.Due to the energy output to the surrounding the energy of reactants will be greater than that of the product, therefore, the reaction will have a negative enthalpy change.Endothermic reactions,on the other hand, are reactions that require additional heat energy from the surrounding. Therefore, the energy of the products will be greater than that of the reactants due to energy input from the environment and thus the enthalpy change will be positive.

Ansa leaf changing color in autumn;

The answer is c. risk