What consideration should be made before implementing this solution?

Northern Trail Outfitters maintains their primary customer identity in their ERP system but managers their customer service via Service Cloud. Customer data is updated in real-time based on changes in the ERP, and the ERP customer ID serves as the Customer Key.

They want to leverage Synchronized Data Extensions to import data about cases from Service Cloud every 15 minutes.

What consideration should be made before implementing this solution?
A . Moving to use the email address as the contact key would simplify the integration since it is common to both systems.
B. Marketing Cloud will deduplicate customers based on their email address, meaning some customers may be overwritten or not receive email.
C. The number of contacts added to the instance will be approximately twice as large by using this integration pattern.
D. They will have to migrate to use Service Cloud IDs, such as the Contact ID, as the contact key instead of ERP IDs.

Answer: D