Final answer:
Entropy is the correct answer. It tells us if a reaction can occur, not how fast it will occur.
Step-by-step explanation:
The correct answer is C. Entropy. Entropy is a thermodynamic property that describes the degree of disorder or randomness in a system. It tells us whether a reaction can occur or not, based on the change in the number of microstates available to the system. Entropy does not provide information about the speed or rate of the reaction, which is determined by the activation energy and other factors.