Which send tracking metric provides the bounce description "Address is non-existent at the domain?

A marketer sent a promotional email to contacts who recently attended a trade show. The data extension used for the send contained 3,100 records. The delivery rate on the send was lower than anticipated. After viewing tracking information, she determined many email addresses were problematic.

Which send tracking metric provides the bounce description "Address is non-existent at the domain?
A . Soft Bounce
B. Blocked Bounce
C. Hard Bounce
D. Undeliverable

Answer: C