You’re currently targeting all inventory in one campaign through an “All products” group. How should you find campaign optimization opportunities?

Understand which creatives perform best in the “Ads” tab
Segment performance by various shopping views through “Predefined reports” in the reporting icon on the top right of your account
Check impressions for each product in Google Merchant Center
See query-level product performance in the “Keywords” tab

The correct answer is:

Segment performance by various shopping views through “Predefined reports” in the reporting icon on the top right of your account.