Final answer:
Things in a directory server are organized hierarchically, meaning data is structured in a layered format like folders within a computer file system, which is practical for network resource management.
Step-by-step explanation:
The way things are organized in a directory server is C) Hierarchically. This means that data is structured in layers, where each layer can have multiple items beneath it, similar to how folders and subfolders work on a computer file system. Unlike organizing alphabetically or by file size, a hierarchical approach allows for a more structured and logically organized way to navigate through the data. This format is practical for managing users, computers, and other resources in a networked environment. Directory servers, such as those that implement the Lightweight Directory Access Protocol (LDAP), employ this hierarchical organization to efficiently manage and retrieve data.