You are developing a YANG-based policy model to encode the type of entity that is connected to a given interface, such as partner, supplier, customer, or distributor. Which YANG statement limits any…

The 'when' statement in YANG defines a dependency for a data node or statement on the existence or value of another node in the data tree, making the configuration action for that node conditional. If the 'when' condition evaluates to false, the node is effectively not allowed to be present in the configuration.

The 'case' statement is used within a 'choice' statement to define mutually exclusive options, not to limit configuration based on arbitrary conditions.

The 'enumeration' statement defines a specific set of allowed string values for a leaf, which limits the data values but not the configuration action itself based on other data.

'contains' is not a standard YANG keyword that limits configuration actions; it describes a conceptual relationship or part of module structure but not a constraint mechanism.