You have a virtual machine that requires a software update. You have not yet tested the update,
so you need a back out plan. If the update fails you want to recover the VM to its current state.
Which of the following features will help you do this in the least amount of time?

A.
Fault Tolerance

B.
vSphere Replication

C.
Snapshots

D.
vSphere Data Protection

Explanation:
http://www.vmware.com/support/ws4/doc/preserve_snapshot_ws.html