Answer: high entropy
Step-by-step explanation:
Entropy is the measure of randomness or disorder of a system.
If a system moves from an ordered arrangement to a disordered arrangement, the entropy is said to decrease and vice versa.
According to second law of thermodynamics, all spontaneous processes lead to increase in entropy.
Thus as rusting is a spontaneous process, it happens on its own, randomness increases and thus entropy also increases.