Which command below will delete the first key?

An administrator has created a mapping with the following command:

cryptsetup luksOpen /dev/sda1 cryptvol

and hat set 3 different keys. Which command below will delete the first key?

A.
cryptsetup luksDelKey /dev/sda1 0

B.
cryptsetup luksDelKey /dev/sda1 1

C.
cryptsetup luksDelKey /dev/mapper/cryptvol 1

D.
cryptsetup luksDelKey /dev/mapper/cryptvol 0