Which two statements are true about the B-tree Index?

Which two statements are true about the B-tree Index?

A.
The leaf blocks in the index are doubly linked.

B.
The leaf node stores a bitmap for each key value.

C.
Rows with a NULL value in key columns also have entries in the Index.

D.
The deletion of a row from the table causes a logical deletion in the index leaf block and the space becomes
available for a new leaf entry.

Explanation:
https://docs.oracle.com/database/121/CNCPT/indexiot.htm#CNCPT88836