(A) Inventory > Ad Exchange rules > Publisher declarations
(B) Admin > Global network settings
(C) Delivery > Creatives
(D) Inventory > Ad Exchange rules > Ad types and backup ads
If you want to change your settings to only serve image ads, you should navigate to Inventory > Ad Exchange rules > Ad types and backup ads within Ad Manager.
This question is a part of the Check your Knowledge section of the “Use Rules and Declarations to Manage Ads” lesson from the “Manage Ads with Rules and Protections” unit which is part of the Drive Advertising Revenue with Google Ad Manager course.