The correct data source is Event because the required Order Number belongs to the purchase event that initiated the marketing interaction. Marketing Cloud Next supports Event as a personalization data source for Email, SMS, and WhatsApp messages . Event-based personalization makes attributes carried by the triggering event available as merge fields within the message.

In this scenario, when the purchase occurs, the triggering event contains contextual transaction information such as the Order Number. The WhatsApp template can reference that event attribute directly without requiring the value to be separately persisted and retrieved through a Data Graph.

A Data Graph is more appropriate when personalization requires persistent customer-profile information or attributes from related Data 360 objects. A Salesforce Record source is appropriate when the content specifically needs fields from a CRM record supplied to the personalization context. Neither is necessary when the desired information originates directly from the event that triggered the message.

The uploaded master bank identifies option C. Salesforce's personalization reference confirms that Event is supported for WhatsApp and can supply event-based attributes to marketing content.

Study Guide Reference: Campaign Design, Flow Orchestration and Content → Content Personalization → Event Data Sources and WhatsApp Messaging.

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