Which two statements are true regarding B-tree index? (Choose two.)

B-tree index leaf blocks in Oracle are organized as a doubly linked list, meaning each leaf block contains pointers to both the previous and the next leaf block, enabling efficient full index scans and range scans in both ascending and descending order.

Storing a bitmap for each key value is the structure used by bitmap indexes, not B-tree indexes; B-tree leaf nodes store individual key values paired with their corresponding ROWIDs.

In Oracle B-tree indexes, rows where all indexed key columns contain NULL values are not stored in the index, which means queries using IS NULL on an indexed column cannot use a standard B-tree index for that condition.

When a row is deleted from a table, Oracle does not immediately remove the corresponding index entry; instead, the entry is marked as logically deleted. The space occupied by that entry can be reused by future inserts into the same block but is not immediately reclaimed or returned to free space.