Which field name should be included in the report in addition to email address?

Northern Trail Outfitters (NTO) wants to send an email to all Contacts who have signed up for its newsletter, but have not joined its loyalty program. NTO has created a report in Sales Cloud which it will select using a Send Flow in Content Builder.

Which field name should be included in the report in addition to email address?
A . Individual ID
B. Contact ID
C. CampaignMember ID
D. External ID

Answer: B