What is the main technical advantage that will be available on a server after installing virtualization technologies such as Xen or KVM ?

What is the main technical advantage that will be available on a server after installing virtualization technologies such as Xen or KVM ?

A.
The execution time of processes which use the CPU intensively will be reduced.

B.
The computing power of the server will be increased.

C.
The number of running kernel instances will be limited to one.

D.
It will be possible to share physical resources between insulated execution environments.

E.
It will be possible to create virtual networks.