Final answer:
Changing the cardinality between data extensions in Contact Builder requires deleting one of the extensions and reviewing any scheduled sends that use filters based on those extensions, as filters do not automatically adapt and contacts may be affected.
Step-by-step explanation:
When Northern Trail Outfitters (NTO) decides to change the cardinality between two data extensions inside Contact Builder, there are consequences that affect their data management. Firstly, to change cardinality, all references to the existing relationship must be removed. This may mean that one of the data extensions must be deleted from the attribute group. Afterward, the relationship can be redefined with the new cardinality. Secondly, any scheduled sends using a filter based on one of the data extensions could be impacted. The filters do not automatically update to accommodate the change in cardinality and, therefore, must be reviewed and potentially redesigned to ensure they still function as intended.