Why is the value set to 4194304 and not to 2516582?

You have executed this command to change the size of the database buffer cache:
SQL> ALTER SYSTEM SET DB_CACHE_SIZE=2516582;
System altered.
To verify the change in size, you executed this command:
SQL> SHOW PARAMETER DB_CACHE_SIZE
NAME TYPE VALUE
———————- —————- ——————
db_cache_size big integer 4194304
Why is the value set to 4194304 and not to 2516582?

A.
Because 4194304 is the granule size

B.
Because 4194304 is the standard block size

C.
Because 4194304 is the largest nonstandard block size defined in the database

D.
Because 4194304 is the total size of data already available in the database buffer cache