An online travel-planning startup wants to serve ads that would be a good fit for both desktop and mobile devices.Which technology can help them achieve that goal?

HTML5 is a versatile format that allows for responsive ad creatives, meaning they can automatically adjust their layout and content to fit various screen sizes and devices, including both desktop and mobile. This ensures a consistent and optimized user experience across platforms. Display & Video 360 Marketplace is a platform for buying ad inventory, not a creative format. Campaign Manager 360 is an ad server and campaign management tool, not a creative technology. Native apps are standalone applications for specific devices, not a format for serving ads across both desktop and mobile web environments.