What does the following btrfs command do?

What does the following btrfs command do?

$ sudo btrfs subvolume snapshot src src-01

A.
Creates snapshots of the src src-01 subvolumes

B.
Creates a snapshot of the src-01 subvolumes in src

C.
Creates the src and src-01 subvolumes and takes a snapshot of these subvolumes

D.
Creates a snapshot of the src subvolumes in src-01

Explanation:
*To create a snapshot use
sudo btrfs subvolume snapshot /mnt/@ /mnt/@_snapshot
this will create a snapshot of the @ subvolume named @_snapshot located also in the top of the
btrfs tree.
*btrfs subvolume snapshot <source> [<dest>/]<name>
Create a writable snapshot of the subvolume <source> with
the name <name> in the <dest> directory.