What is a 'Materialized View'?

1. A A standard, virtual SQL View that provides a logical window into the data without consuming any additional physical storage space on the disk array.
2. B A specialized user interface component that dynamically renders the database schema as a visual graph for administrator-level cluster management.
3. C A redundant, off-site backup of the entire database state that is strictly synchronized using a high-latency asynchronous mirroring protocol.
4. D A physically stored, pre-calculated query result that offers rapid read access but must be refreshed periodically as the underlying base data changes.