Which of the following is NOT one of the common types of ground treatments used to enhance ground resistance?

The choice identified as the correct answer, potassium chloride, is not typically considered one of the common types of ground treatments used to enhance ground resistance. Ground treatments are typically employed to decrease the ground resistance in electrical systems, and common options include materials that improve soil conductivity.

Magnesium sulfate, copper sulfate, and rock salt are all widely used in grounding applications. These substances help to lower the resistivity of the soil around grounding electrodes, promoting better electrical conductivity. Magnesium sulfate and copper sulfate, for example, provide ions that facilitate better moisture retention and conductivity in the soil. Rock salt, on the other hand, also dissolves in water to create an electrolyte solution, contributing to improved ground contact.

While potassium chloride has applications in agriculture and sometimes in certain industrial processes, it is not recognized in the same way for grounding applications as the other materials listed. Thus, in the context of enhancing ground resistance, potassium chloride does not play a common role.