When memory is overcommitted, which two values can an administrator vary to increase the
amount of physical memory granted to a given virtual machine? (Choose two.)

A.
Idle Memory Tax

B.
Shares

C.
VMMEMCTL

D.
Memory Reservation

Explanation:
http://pubs.vmware.com/vsphere-50/topic/com.vmware.ICbase/PDF/vsphere-esxivcenter-server-50-resource-management-guide.pdf