The factors on which the amount of energy absorbed by an endothermic reaction depends are the " physical state of the reactant and the difference in the potential energy of the reactant and the product".
Explanation:
In an endothermic reaction the factors that affects the reaction are the physical state of the reactant, which thus becomes the enthalpy. And the difference in potential energy of the reactant because if the sum of the potential energy is less than the sum of the potential energy of the product than the endothermic reaction will be positive and the reaction hence will be endothermic.
Answer: the answer should and most definitely be D.
Explanation: I mean think about it after a while only a few radioactive nuclei are left which means it will dye down after a while which also makes it very boring hope this helps :)