Which Dataverse column stores a single record reference

The qualifier that decides it: "single related record" The first requirement asks for a reference to exactly one related record, explicitly "without performing any aggregations." That phrase alone eliminates option C (Rollup), because a rollup column exists precisely to aggregate related rows — count, sum, min, max — on a recurring schedule. Option B (Calculated) is also disqualified: it evaluates an expression over fields on the same record or across related records to produce a derived value, so it is not a plain pointer to one record either.

"Part of the table definition" and automatic maintenance The second requirement says the link must be stored in the table definition and maintained by the platform. That is the exact definition of a Dataverse lookup column: configuring it creates a formal relationship between the table and a target table, and the platform keeps the reference consistent when records are created, reparented or deleted. Option A (Formula) fails here — a formula column computes a text, number or date value on demand and never registers a relationship in the schema, so no schema-level link exists to maintain.

What the comments reinforce One contributor notes that a Lookup column "references a single record from a target table and automatically creates and maintains a formal database relationship within the Dataverse schema, without performing any data aggregation," and a second repeats that it is used "to reference a single related record in another Dataverse table." Both map directly onto the two stated requirements, with no aggregation and no derived-value evaluation.

Conclusion Option D (Lookup) satisfies both constraints simultaneously; A, B and C each violate at least one of them.