Northern Trail Outfitters received a complaint today from a customer who received an email after unsubscribing last week. Today's email was sent using Marketing Cloud Connect (MCC), though last week was sent when an external system dropped a file on the Marketing Cloud SFTP andTriggered a User-Initiated Send through an automation.What could be the reason the customer received the email through MCC?
选项：

A: The previous send's user needed to have edit permissions in Salesforce,
B: Email Opt Out is only updated if the send originates in Salesforce.
C: The previous send used Email Address as a Subscriber Key.
D: The Email Opt Out field needs to be added to the Contact Page Layout.