What is 'Index Bloat' in MVCC databases like PostgreSQL?

1. A A specialized architectural failure where indexes begin to store massive binary data blobs (LOBs) that were intended for the primary table storage.
2. B A condition where frequent updates create 'dead' version entries in the index that cannot be reclaimed until a vacuum or maintenance routine is executed.
3. C When the database's internal transaction log overflows and begins writing raw metadata directly into the index storage blocks to prevent data loss.
4. D When the total number of indexes on a single table exceeds the database's hard limit, causing the engine to revert to a less efficient storage format.