All client computers in your company run Windows 7. Windows Virtual PC is installed  on all client computers.
You create and configure a virtual machine (VM) named Guest1.
You need to use the Guest1 virtual hard disk (VHD) as a base for additional VMs that will run on the same host computer, and minimize the disk space required for each ne w VM.
Which type of VHD should you create for the new VMs?（）