The correct answer is D, because:

In Salesforce Marketing Cloud, to capture unsubscribe statuses across all Business Units (BUs) in an Enterprise 2.0 account, the system data view _BusinessUnitUnsubscribes must be used.

_BusinessUnitUnsubscribes provides unsubscribe event data across all business units, showing which subscriber unsubscribed, in which BU, and when — making it ideal for consolidated enterprise-level reporting or synchronization to external systems like a CRM.

Official Salesforce documentation states:

"_BusinessUnitUnsubscribes: Returns a record for each unsubscribe event, per business unit, providing a view of the unsubscribe status at a BU level. This view is used primarily in Enterprise 2.0 accounts to track unsubscribe activity across multiple business units."

(Source: Salesforce Marketing Cloud Official Data Views Documentation)

Key Points from Documentation:

_Subscribers (Option B) gives general subscriber data (status like Active, Bounced, Held), but does not track individual unsubscribe events per BU.

_Unsubscribe (Option C) focuses on unsubscribes but not separated by Business Unit context (which is needed here).

_Complaint (Option A) tracks email complaints, not unsubscribes.

Reference Extract:

"_BusinessUnitUnsubscribes includes SubscriberKey, BusinessUnitID, JobID, ListID, BatchID, EventDate, and EventType (Unsubscribe) for each event where a subscriber opts out of communication at the business unit level."

(Source: Salesforce Marketing Cloud SQL Data Views Guide)

Thus, D (_BusinessUnitUnsubscribes) is the correct choice for syncing unsubscribe data consolidated across all business units to an external CRM.