You should use Bumper ads to see the value in remarketing to audiences who saw it with memorable, shorter video ads.

• In-feed video ads
• Non-skippable in-stream ads
• Masthead ads
• Bumper ads

The correct answer is: Bumper ads

Explanation: To achieve the goal of remarketing to audiences who saw a 30-second video ad with shorter video ads, Bumper ads are the recommended format. These are non-skippable, six-second in-stream ads that are designed to work for a mobile-first world, delivering more reach than any other ad format. Bumpers are bought on a target cost-per-thousand impressions through Google Ads, Display & Video 360, or Google Preferred. They deliver high attention, comparable brand impact, and have a high completion rate. Remarketing with bumper ads to audiences used in longer campaigns can help build frequency and increase lift in brand awareness for new and lapsed customers.