A snapshot is a frozen, read-only image of the entire Data ONTAP active file system that reflects the state of
the ____________ at the time the snapshot was created.

A.
qtrees

B.
volume

C.
directory

D.
storage system

Explanation:
http://backdrift.org/man/netapp/man1/na_snap.1.html
Snapshots can be made of volumes or aggregates; most commonly the former. The question refers to a file
system, or more specifically a volume.
You cannot snapshot directories or qtrees alone.