A. A Hyper-V snapshot works by saving a backup of the VM’s configuration and, if the VM is running at the time, its memory and supporting processes. Hyper-V then creates a differencing disk, which all further disk writes are recorded to, leaving the content of the original disk unmodified after the point when you took the snapshot.
If a pass-through disk is used, the VM is directly accessing a volume instead of a Virtual Hard Disk (VHD). In this case, Hyper-V can’t create a differencing disk, so there’s no way to protect the state of the disk at the time you take the snapshot. Because the disk’s state can’t be preserved, you can’t take snapshots if you’re using pass-through disk access.