How does fault tolerance provide continuous availability?

A.
By providing the availability required by most applications running in virtual machines,
independent of the operating system and application running in it.

B.
By using a feature called Changed Block Tracking (CBT), which backs up content.

C.
By creating and maintaining a secondary virtual machine that is identical to primary
machine.

D.
By using the host as the medium to provide asynchronous replication of datastores.