In most dumps suggested answers are wrong.
The game is to find in the documentation the proof they are wrong.
Play the game...

Regards
Michel

in my opinion there should be 'DELETE EXPIRED' instead of 'UNCATALOG'

An approach towards problem solving that I always take (in addition to searching the docs) is to make simple tests. For example, have you tried the answers? This is E,

RMAN> delete unavailable;

RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-00558: error encountered while parsing input commands
RMAN-01009: syntax error: found "unavailable": expecting one of: "archivelog, backu
ired, force, foreign, global, noprompt, obsolete, proxy, script"
RMAN-01007: at line 1 column 8 file: standard input

RMAN>

So E is definitely wrong.

You haven't tried to run UNCATALOG, have you.

As I said, you only know if you can point to the information inside the documentation (or completly tested the commands/options/...), otherwise it is just a guess.

Regards
Michel

for me there was three correct answers

what is your quest?

The question asks which command(s) will "remove the deleted backups from the recovery catalog". There is only ONE command listed which will do this, and that is A. The ambiguity comes in D. There is no command UNCATALOG, but there is an argument UNCATALOG that you can apply to the command CHANGE, which is another way of removing entries from the catalog.