What is server immutability?

What is server immutability?

A.
Not updating a server after creation.

B.
The ability to change server counts.

C.
Updating a server after creation.

D.
The inability to change server counts.

Explanation:
… disposable upgrades offer a simpler way to know if your application has unknown dependencies. The underlying EC2
instance usage is considered temporary or ephemeral in nature for the period of deployment until the current release is
active. During the new release, a new set of EC2 instances are rolled out by terminating older instances. This type of
upgrade technique is more common in an immutable infrastructure.
https://d0.awsstatic.com/whitepapers/overview-of-deployment-options-on-aws.pdf