- Time spent on site
- Page depth
- Cost-per-click
- Cart size
The correct answer is: Cart size
Explanation: “Cart size” is a prominent example of a metric used to measure value in digital advertising. Through value-based bidding, advertisers prioritize auctions that offer the highest conversion value. Cart size represents the monetary or business value brought by a customer. Bidding with an emphasis on cart size can be a practical first step in effective consumer segmentation. It also accommodates potential sales of a diverse array of products through a single ad click. “Conversions with Cart Data” is a feature that sheds light on purchases made after ad clicks, highlighting top sellers and items most likely to convert.
Read more here: https://support.google.com/sa360/answer/9455757