Air conditioning systems are categorized by their air cooling and distribution methods. Unitary systems are compact, self-contained units, such as window or split ACs, designed for individual rooms. Self-contained systems are also single-unit systems containing all components, serving specific zones. Central station systems are extensive installations that condition air for entire buildings via ductwork. An automatic expansion system is not a type of air conditioning system; it denotes an automatic expansion valve within a refrigeration cycle, which controls refrigerant flow. Consequently, it is a component, not a complete air conditioning system. Therefore, option (D) is accurate.