Which architectural principle describes provisioning resources on demand and releasing them when they are no longer required?

Elasticity is the correct answer because it refers to the ability of a system to automatically scale resources up or down based on demand. This means provisioning resources when needed and releasing them when no longer required, optimizing cost and performance. High availability ensures a system remains operational despite failures, but doesn't specifically address dynamic scaling. Decoupled architecture separates components so they can operate independently, improving fault tolerance and scalability, but isn't about resource provisioning on demand. Resilience is the ability of a system to recover from failures and maintain functionality, which is related to high availability but not the core concept of dynamic resource allocation.