A customer wants to integrate a new dataset with pre-existing contacts.

Because the new dataset is refreshed independently, on its own separate feed cadence, from the main contact data, it should live in its own dedicated data extension rather than being merged directly into the core contact record. In Data Designer, this new data extension is then linked (related) to the existing contact-based data extensions through a defined relationship on a common key, allowing the data to be joined for segmentation, personalization, and decision-split logic while preserving each source ' s independent update lifecycle. This relational approach is precisely what Data Designer is built for — modeling one-to-one or one-to-many relationships between separately-maintained data extensions without collapsing them into a single monolithic table. Option A ' s ' new population ' terminology does not correspond to a real Data Designer configuration concept — Data Designer works in terms of related data extensions, not ' populations. ' Option B unnecessarily specifies a ' Salesforce data extension ' (implying a synchronized object from a connected org), which is not indicated anywhere in the scenario and adds an unsupported assumption. Option D, adding attribute fields directly to the contact record, would break the independent-feed requirement, since the contact data extension and the new dataset are updated on different schedules and by different sources. Reference: Data Designer, Data Extension Relationships.