Northern Trail Outfitters recently purchased Marketing Cloud to start running cross-channel campaigns.

Comprehensive and Detailed Explanation:

The correct answers are B and D.

B — CRM ID: A unique identifier across CRM and Marketing Cloud.

D — Loyalty Program Number: Another strong candidate for subscriber key if it is unique across systems.

Important! Subscriber Key must be unique, non-changing, and consistent across channels.

❌ Why others are wrong:

A: Email can change over time; using email address as Subscriber Key can cause serious identity issues.

C: Mobile Device ID is specific to mobile channels, not a cross-channel identifier.

Exact Extract from Salesforce Official Documentation:

Salesforce Help — Subscriber Key Best Practices:

"The subscriber key should be a unique, unchanging identifier such as a CRM ID or Loyalty ID to maintain consistent cross-channel communication."

(Source: https://help.salesforce.com/s/articleView?id=sf.mc_es_subscriber_key_best_practices.htm )

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