Which component should be discussed with the customer to allow for this use case?

A financial services customer states that families often share email addresses across multiple checking, savings, loan, and credit accounts. The customer needs to allow individual accounts to use the same email address in Marketing Cloud but maintain separate subscriber attributes.

Which component should be discussed with the customer to allow for this use case?
A . Subscriber Key
B . Contact ID
C . Member Record
D . Data Extensions

Answer: A