What key issue should be addressed?

A retail company’s database of record resides at a 3rd-party company that also keeps track of purchase history.

That database only updates once a day where new records can be created and merged.

The database uses an "Email ID," which is a numeric field that represents both the business unit and email address.

The company now wants to be able to send real-time Welcome emails to people (newly registered website users) who provide their email address in exchange for getting 10% off their first order, and ensure this send is connected to "Email ID" in the database.

What key issue should be addressed? Choose 3 Answers
A . How will Marketing Cloud and the database sync up?
B. Will new users have an "Email ID"?
C. What will be used as Subscriber Key?
D. What publication lists will be used?
E. Will the company need a custom preference center?

Answer: A,B,C