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