For a clothing company interested in tracking shoppers who first saw their ad on a mobile app and then made a purchase using their personal tablet, the appropriate Display & Video 360 measurement to use is cross-environment conversions.

• Conversion tracking
• Same-device measurement
• Open measurement software development kit (SDK)
• Cross-environment conversions

The correct answer is: Cross-environment conversions

Explanation: Cross-environment conversions offer insight into the effectiveness of advertising campaigns across various platforms and devices, such as tablets, mobiles, and desktops, and both app and web environments. By linking cookies, resettable device IDs, and aggregated sign-in data, this measurement can identify a user’s journey from ad exposure to conversion across different environments, enhancing the understanding of campaign impact without retaining specific user data.

Chapter 25: Get Started with Ads in Mobile App Inventory

Read more here: https://support.google.com/displayvideo/answer/6155943