You notice a high number of waits for the db file scattered read and db file sequential read events in the recent Automatic Database Diagnostic Monitor (ADDM) report. After further investigation, you find that queries are performing too many full table scans and indexes are not being used even though the filter columns are indexed. Identify three possible reasons for this.（）

• A、Missing or stale histogram statistics
• B、Undersized shared pool
• C、High clustering factor for the indexes
• D、High value for the DB_FILE_MULTIBLOCK_READ_COUNT parameter
• E、Oversized buffer cache