Which memory allocation technique allows physical memory to be reclaimed from
virtual machine A and redistributed to virtual machine B, possibly forcing virtual
machine A to swap internally?

A.
Transparent Page Sharing

B.
Memory Balloon Driver

C.
VMkernel Swap

D.
RAM Overcommit

Explanation:
Memory Provisioning Recommendations for VMware Infrastructure 3 Operational Best
Practices, page 7

Memory Ballooning

Memory ballooning is handled through a driver (vmmemctl.sys) that is installed as part
of the VMware Tools. This driver is loaded in the guest OS to interact with the VMkernel
and is leveraged to reclaim memory pages when ESX memory resources are in demand
and available physical pages cannot meet requirements. When memory demands rise on
the ESX host, the VMkernel will instruct the balloon driver to “inflate” and consume
memory in the running guest OS, forcing the guest operating system to leverage its own
native memory management techniques to handle changing conditions.