Windows Registry consists of multiple root keys called

Concept: The Windows Registry is a hierarchical database of configuration data organized into a small set of top-level predefined keys (e.g. HKEY_LOCAL_MACHINE, HKEY_CURRENT_USER, HKEY_USERS, HKEY_CLASSES_ROOT, HKEY_CURRENT_CONFIG). Physically, this data is not one single file — it is stored on disk as discrete file-backed groupings of keys, subkeys, and values, and each such grouping is called a hive.

Strictly, Microsoft's own terminology distinguishes the two: the top-level HKEY_* nodes are called predefined (root) keys, while hive specifically names the file-backed storage groupings that back those keys on disk. This item's stem uses the common, looser exam convention of calling those persisted root-level groupings "hives" — and among the four offered options, hive remains the only term Microsoft's documentation actually uses for the registry's key-groupings, so it is the best-supported answer here.

• Tables — denotes a row/column data structure (e.g. a database table); the registry’s root groupings are not organized as rows and columns.

• Folders — denotes a file-system directory used to group files on disk; the Registry Editor’s tree view visually resembles folders, but the underlying storage/organizational unit is a hive, not a filesystem folder.

• Clusters — denotes the fixed-size disk-allocation unit a file system uses to store file data; this is a storage-layer concept unrelated to the registry’s logical root groupings.

Cross-check: Microsoft’s official Win32 documentation ("Registry Hives") defines a hive as "a group of keys, subkeys, and values in the registry that has a set of supporting files," and lists the standard root hives (SAM, SECURITY, SOFTWARE, SYSTEM, DEFAULT, etc.) under exactly this term — confirming Hives, not Tables, Folders, or Clusters, as the term used for the registry’s root-level key groupings.