What definition is covered under the category for sewage systems?

The category for sewage systems is best defined by "Sewage Disposal Methods." This encompasses a variety of processes and techniques used to manage and eliminate sewage from residential, commercial, and industrial sources. Sewage disposal systems are designed to collect, transfer, treat, and ultimately discharge or recycle sewage safely and effectively to protect public health and the environment.

When considering the other choices, "Soil" refers to the natural ground material that can play a role in absorbent sewage systems but is not a definition of sewage systems themselves. "Wastewater Treatment" is certainly relevant to the broader field as it involves processing sewage after it has been generated, but it is a subset of sewage disposal methods rather than a definition of the entire category. "Sludge Management" pertains to the handling of the byproducts from wastewater treatment and is not a comprehensive definition of sewage systems as a whole. Thus, the correct answer focuses specifically on the overall methods employed for sewage disposal.