A: Setting a PDB resource plan is optional. If not specified, all sessions within the PDB are treated equally.
* In a non-CDB database, workloads within a database are managed with resource plans.
In a PDB, workloads are also managed with resource plans, also called PDB resource plans.
The functionality is similar except for the following differences:
/ Non-CDB Database
Multi-level resource plans
Up to 32 consumer groups
Subplans
/ PDB Database
Single-level resource plans only
Up to 8 consumer groups
(not B) No subplans

References: https://docs.oracle.com/cd/B28359_01/server.111/b28320/initparams240.htm#REFRN10214

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).