The correct answer is: A. A lowering of entropy
Entropy is a measure of the disorder or randomness of a system. A spontaneous change is one that occurs without any outside intervention. In other words, it is a change that happens on its own. Spontaneous changes always occur in the direction of increasing entropy. This is because entropy is always increasing in the universe.
Option B is incorrect because a lowering of free energy is not always a spontaneous change. For example, a reaction that is exothermic (releases heat) will have a decrease in free energy, but it may not be spontaneous if the activation energy is too high.
Option C is incorrect because an increase in free energy is never a spontaneous change. This is because the second law of thermodynamics states that the entropy of an isolated system always increases over time. If the free energy of a system increases, then the entropy must also increase.
Option D is incorrect because an increase in internal energy is not always a spontaneous change. For example, a reaction that is endothermic (absorbs heat) will have an
increase in internal energy, but it may not be spontaneous if the activation energy is too high.In conclusion, the only option that is always true for a spontaneous change is a lowering of entropy.