An advertiser wants to drive cost-effective in-app purchases from existing app users. Which bidding solution is recommended for this demand gen objective?

CPA (cost-per-action) is the recommended bidding solution because the advertiser's objective is to drive cost-effective in-app purchases, which are specific actions. CPA bidding optimizes for conversions (in this case, in-app purchases) at a target cost, directly aligning with the goal of maximizing purchases while controlling costs. tCPV (cost-per-view) optimizes for video views, not specific in-app actions. Viewability with Active View measures whether an ad is seen, but doesn't optimize for conversions. Target CPM optimizes for impressions at a target cost per thousand, which is suitable for brand awareness but not for driving specific in-app purchases.