B) Email tracking for messages sent from the ecommerce site will not be replicated via Marketing Cloud Connect and therefore will not be visible to the Service Agents. Marketing Cloud Connect can only track email sends that are initiated from Marketing Cloud or Salesforce CRM, not from an external ecommerce site. This means that the Service Agents will not have a complete view of the customer's email interactions or preferences. D. Contacts may be duplicated in Marketing Cloud during the transition phase, and additional work may be required to merge identities at a later date. Marketing Cloud Connect uses the Salesforce Contact ID or Lead ID as the contact key in Marketing Cloud, which is a unique identifier for each contact or lead. If the existing ecommerce site integration uses a different identifier, such as email address or customer ID, then it may create duplicate contacts in Marketing Cloud when syncing with Service Cloud. This can affect the contact count, billing, and personalization in Marketing Cloud. Reference: https://help.salesforce.com/s/articleView?id=sf.mc_co_sync_leads_and_contacts.htm&type=5 https://help.salesforce.com/s/articleView?id=sf.mc_co_subscriber_key_migration.htm&type=5