Explanation
B (not C): You can validate that all database files and archived redo logs can be backed up by running a command as follows:
RMAN> BACKUP VALIDATE DATABASE ARCHIVELOG ALL;
This form of the command would check for physical corruption. To check for logical corruption, RMAN> BACKUP VALIDATE CHECK LOGICAL DATABASE ARCHIVELOG ALL; D: You can use the VALIDATE keyword of the BACKUP command to do the following:
Check datafiles for physical and logical corruption
Confirm that all database files exist and are in the correct locations.
Note:
You can use the VALIDATE option of the BACKUP command to verify that database files exist and are in the correct locations (D), and have no physical or logical corruptions that would prevent RMAN from creating backups of them. When performing a BACKUP...VALIDATE, RMAN reads the files to be backed up in their entirety, as it would during a real backup. It does not, however, actually produce any backup sets or image copies (Not A, not E).

Schema objects are referenced with varying usage patterns; therefore, their cache behavior may be quite different.
Multiple buffer pools enable you to address these differences. You can use a KEEP buffer pool to maintain objects in
the buffer cache and a RECYCLE buffer pool to prevent objects from consuming unnecessary space in the cache. When
an object is allocated to a cache, all blocks from that object are placed in that cache. Oracle maintains a DEFAULT
buffer pool for objects that have not been assigned to one of the buffer pools.

Note:
Providing a UNIX Group Name
If you are installing a product on a UNIX system, the Installer will also prompt you to provide the name of the group
which should own the base directory.
You must choose a UNIX group name which will have permissions to update, install, and deinstall Oracle software.
Members of this group must have write permissions to the base directory chosen.
Only users who belong to this group are able to install or deinstall software on this machine.

E: Performance is improved by load balancing across multiple network interfaces (if available).
Note:
*To enable Direct NFS Client, you must replace the standard Oracle Disk Manager (ODM) library with one that supports Direct NFS Client.
Incorrect: Not A: Direct NFS Client is capable of performing concurrent direct I/O, which bypasses any operating system level caches and eliminates any operating system write-ordering locks Not B:
*To use Direct NFS Client, the NFS file systems must first be mounted and available over regular NFS mounts.
*Oracle Direct NFS (dNFS) is an optimized NFS (Network File System) client that provides faster and more scalable access to NFS storage located on NAS storage devices (accessible over TCP/IP). Not D: Direct NFS is provided as part of the database kernel, and is thus available on all supported database platforms - even those that don't support NFS natively, like Windows.
Note:
*Oracle Direct NFS (dNFS) is an optimized NFS (Network File System) client that provides faster and more scalable access to NFS storage located on NAS storage devices (accessible over TCP/IP). Direct NFS is built directly into the database kernel - just like ASM which is mainly used when using DAS or SAN storage.
*Oracle Direct NFS (dNFS) is an internal I/O layer that provides faster access to large NFS files than traditional NFS clients.