Why does HR still see the old data?

The user SCOTT executes the following command successfully to increase the salary values in
one of his sessions:

SQL> UPDATE emp SET sal=sal*1.15 WHERE deptno=20;
Before SCOTT ends the transaction, user HR who has the privileges on EMP table executes a
query to fetch the salary details but finds the old salary values instead of the increased values.
Why does HR still see the old data?

The user SCOTT executes the following command successfully to increase the salary values in
one of his sessions:

SQL> UPDATE emp SET sal=sal*1.15 WHERE deptno=20;
Before SCOTT ends the transaction, user HR who has the privileges on EMP table executes a
query to fetch the salary details but finds the old salary values instead of the increased values.
Why does HR still see the old data?

A.
because of redo data from redo log file

B.
because of data from a temporary tablespace

C.
because of undo data from the undo tablespace

D.
because of data from database buffer cache

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