PostgreSQL's GiST (Generalized Search Tree) allows indexing what kind of data?

1. A Only standard integer and numeric data types that have a clearly defined, linear mathematical sort order within the database schema.
2. B Large binary blobs (LOBs) that require high-speed cryptographic signatures to ensure data integrity across various disparate partitions.
3. C Individual keys within deeply nested JSON structures to enable O(1) retrieval speeds for schema-less document-based data processing.
4. D Arbitrary complex types (Geometric shapes, IP Ranges) where the concept of 'ordering' is defined by spatial overlap or logical containment rules.