Under What Conditions Can You Dynamically Change the Number of VCPUs

Under what conditions can you dynamically change the number of vCPUs or memory available to a guest OS?

A) The host's hardware must support hot add features via VT-x.
B) The host must be using a type-2 hypervisor.
C) The guest OS must be installed in a UEFI enabled VM.
D) The guest OS must support the dynamic addition of CPUs and memory.