A book publisher is releasing the newest novel from a well-known author and creating four unique 30-second videos to promote the book. They tasked you to identify which ad viewers watch to the end most often. To prioritize showing that ad, what type of video creative optimization would you use in Display & Video 360?

Optimizing for completions directly addresses the publisher's goal of identifying and prioritizing ads viewers watch to the end. This optimization strategy instructs Display & Video 360 to favor serving video creatives that demonstrate a higher completion rate, ensuring the most engaging video is shown more frequently. "Optimize for clicks" would prioritize videos that generate more clicks, which isn't the primary goal here. "Optimize for time spent on-screen" focuses on overall view duration, not necessarily full completions. "Optimize for conversions" would be relevant if the goal was to drive specific actions like book purchases, but the question specifically asks about identifying which ad viewers watch to the end.