Your question looks a bit incomplete as you have the same contents in options a) and d). According to your list, I can't see the correct answer, but I can give you one.The difference between the potential energy of the products of the potential energy of the reactants is equal to the enthalpy of the reaction.
Answer:
A. a system that can be affected by the outside environment, by an exchange of matter or energy
C. A central body is the center of the universe.
