What list email or email template report deliverability metric could indicate an unverified sending domain?

What factors are involved with and determine email deliverability?
(Choose 2)

Which two actions can be used to change a prospect's Pardot campaign? (Choose two answers.)

A Pardot user sends out a list email and notices that as a result of the email send, many prospects are now marked as 'Do Not Email'. What metrics in the list email report could help the Pardot user understand how these prospects may have become unmailable?

A Pardot administrator wants to use progressive profiling to collect information on a prospect over time.
What It the recommended Pardot asset to use?