For determining which 30-second video promoting your company’s new restaurant opening is watched to the end most often, you should utilize the “Optimize for completions” video creative optimization in Display & Video 360.

• Optimize for time spent on-screen
• Optimize for conversions
• Optimize for clicks
• Optimize for completions

The correct answer is: Optimize for completions

Explanation: The “Optimize for completions” strategy prioritizes video creatives expected to fully engage viewers, ensuring they are both audible and viewable upon completion. This optimization uses playback data to deliver ads more frequently into ad auctions or guaranteed deals when they are anticipated to meet audibility and viewability criteria at the end of playback. This method, also referred to as Audibility and Viewability On Completion (AVOC), helps ensure the most engaging ads are shown to your audience, enhancing the impact of your promotional videos.

Read more here: https://support.google.com/displayvideo/answer/7558640