A management domain typically contains a large amount of management information. Each individual item of（） information is an instance of a managed object type. The definition of a related set of managed （72）types is contained in a Management Information Base (MIB)module. Many such MIB modules are defined. For each managed object type it describes, a MIB （73） defines not only the semantics and syntax of that managed object type, but also the method of identifying an individual instance so that multiple （74） of the same managed object type can be distinguished. Typically, there are many instances of each managed object （75） within a management domain

A. rotation

B. switch

C. management

D. transmission