Which parameter is set to read-only for the parent virtual machine's disk?

The parameter that is set to read-only for the parent virtual machine's disk is the ParentDisk.vhdx. In a virtualization environment, the parent disk is typically the original disk image used when creating child virtual machines or snapshots. Setting the parent disk to read-only ensures that the original data remains unchanged while allowing the child virtual machines to make modifications to their own copies of the disk.

This practice prevents any alterations to the base image, preserving the integrity of the parent disk. Child disks will be created as differencing disks that track changes made relative to the parent disk. Hence, making the parent disk read-only is crucial for maintaining a stable and consistent system as it serves as the foundation for the virtual machine hierarchy.

The other options provided do not represent the read-only parent disk in this context. ServerParent.vhd could be an instance of a parent disk but doesn't necessarily indicate it's set to read-only. Test1.vhd and Test2.vhdx may be child disks or entirely different virtual disks that are not subject to read-only restrictions of the parent disk.