问题：

[单选]

You have a Windows Server 2008 R2 Hyper-V server. You take periodic snapshots of your virtual 
machines （VMs） when the VMs are not running. You delete several snapshots from the snapshot tree of a VM. The .avhd files that are associated with the deleted snapshots are not deleted from the volume where the VHD files are stored. You need to ensure that the .avhd files are deleted.
What should you do？（）

A . Reset the VM.
B . Pause the VM.
C . Export the VM.
D . Shut down the VM.