How can a gift officer determine if an acknowledgment letter was sent for a donation?

How can a gift officer determine if an acknowledgment letter was sent for a donation?
A . Check the Status picklist value on the Task object.
B. Check if the Campaign Member status is set to "Acknowledged".
C. Check the Acknowledgement Status picklist value on the Opportunity object.
D. Check the Acknowledgement Status picklist value on the Contact object.

Answer: C