How could they communicate this to all Pardot prospects?

"LenoxSoft is releasing a critical system change that requires their customers to take action in order to avoid service interruption.

How could they communicate this to all Pardot prospects?
A . Send an automated operational email to all prospects.
B. Send Engage emails to all prospect who are opted in.
C. Send a list email to all prospects who are opted in.
D. Send an operational email to all prospects.

Answer: D