Synchronized Data Extensions, delivered through Marketing Cloud Connect, replicate Salesforce object data into Marketing Cloud on a near-real-time cadence (well within the stated 30-minute tolerance) and scale to millions of records without the manual scheduling overhead of report-based imports. Critically, Synchronized Data Extensions support a filter condition at setup, so the consultant can configure the sync to include only records where the consent checkbox equals true — satisfying the requirement that just the opted-in half of the customer base is brought over, rather than importing everything and filtering downstream. Salesforce Report Import via Automation Studio (A) is a scheduled, batch-oriented process typically running on an hourly-or-longer cadence and does not reliably guarantee a 30-minute SLA at this scale, nor does it filter as cleanly as a native sync filter. Event Data from a Journey Builder Entry Event (B) is designed to trigger journey entry from a Salesforce event (like a Platform Event or Process Builder/Flow action), not to bulk-import and maintain a filtered customer dataset for general use across multiple journeys. ' All Subscribers ' (D) is the legacy subscriber list, not a Salesforce-synchronized, filterable dataset, and the claim that it is synchronized in real time is inaccurate. Reference: Marketing Cloud Connect, Synchronized Data Extensions.