A measure of the disorder of a system is called:

enthalpy

energy

entropy

synergy

The answer is Entropy or part C.

Entropy is basically a thermodynamic quantity that tells the randomness of a system or as said in the question tells us a measure of the disorder of the system.

The second law of thermodynamics states that a closed system has entropy which may remain constant or otherwise might increase.

It is basically the measure of the change of a system or universe when it goes from order to disorder.

The entropy of a system is the measure of its level of disorder, over time the entropy of any given system will increase.