Which of the following is not a cloud deployment model?

The correct answer is "Open" because it is not recognized as a formal cloud deployment model within the frameworks established in cloud computing. The three established models of cloud deployment are private, public, and hybrid.

A private cloud is designed for exclusive use by a single organization, allowing for greater control over resources and security. A public cloud is available to multiple entities and is owned and operated by third-party service providers, offering scalability and lower costs. A hybrid cloud combines elements of both private and public clouds, providing flexibility in data management and deployment strategies.

"Open," while it may refer to principles of interoperability or open-source technologies used within cloud environments, does not stand as a distinct category of cloud deployment. This understanding clarifies why "Open" is the response that does not align with recognized cloud deployment models.