When should an advertiser, who's using Campaign Manager 360 to run an in-stream video ad campaign, consider activating default ads for placement?

Analysis of Correct Answer(s) - A default ad in Campaign Manager 360 acts as a fallback or a "catch-all" ad. Its purpose is to serve when no other ad assigned to the placement is eligible for a specific impression. This can happen for various reasons, such as targeting mismatches, frequency caps being met, or browser incompatibility. - By activating a default ad, the advertiser ensures that an impression is always served, preventing blank ad space and fulfilling commitments to the publisher. This is a crucial best practice for maintaining campaign delivery and performance. - Since the default ad must be able to serve in any situation where the primary ad cannot, it should be considered for placements targeting any user or device. For an in-stream video campaign, if a user's browser or device cannot play the video, a compatible default ad (like a standard image) can serve in its place, guaranteeing the impression is filled.

Analysis of Incorrect Options - When serving ads to only tablet/desktop/mobile users: These options are too restrictive. The need for a fallback ad is not exclusive to a single device type. Technical issues or targeting limitations can prevent a primary ad from serving on any device. Therefore, using a default ad is a universal best practice, not one confined to campaigns targeting only mobile, tablet, or desktop users.