Which principle determines object access based on classification level in a mandatory access control model?

The principle that determines object access based on classification level in a mandatory access control model is correctly identified as the Need to Know.

In a mandatory access control (MAC) environment, access to resources is strictly controlled based on the classification levels assigned to both the users and the data. The Need to Know principle dictates that users are granted access to information only if they require it for their specific duties. This ensures that individuals do not have access to sensitive information unless their role necessitates it, enhancing data security by limiting access.

Clearance, while related, is about the authorization level assigned to an individual that allows them to access information at or below that clearance level. However, it doesn't emphasize the necessity of having a reason to access each specific piece of information.

Separation of duties is a principle intended to reduce the risk of fraud or error by distributing tasks and privileges among multiple individuals, which is different from access control based solely on classification.

Ownership pertains to the rights and privileges associated with data management and doesn’t specifically govern access based on classification in a mandatory framework.

Thus, the Need to Know principle is essential in a mandatory access control model for determining who can access data based on its classification level.