The Potential Energy diagram given represents a spontaneous reaction and this means that is an exothermic reaction because it releases more energy in the products than in the reactants.
Enthalpy change has the following formula:
You can realize that in the diagram, the products are minor then the reactants, so this means that the enthalpy change is negative.
In conclusion, the reaction is exothermic and has a negative enthalpy change, the option is C.