你的客戶是運動休閒品牌，他們想知道哪款瑜珈褲的銷量最高。請問他們應在 Search Ads 360 的 Floodlight 資料欄中設定下列哪一個項目，才能在下個節慶購物季到來前，掌握更多轉換相關資訊？

Custom metrics are the correct choice because they allow you to track specific numerical values from your Floodlight tags, such as the quantity of a particular product sold. This directly addresses the client's need to identify the highest-selling yoga pants. Custom variables, while useful for segmenting data, typically track non-numerical attributes like product ID or category, not the sales volume itself. Budget bid strategies are for optimizing bids, not for tracking conversion details. Conversion cart data provides information about the entire cart, but a custom metric can be more granular for a specific product's sales quantity.