How are Shopping ads created? 

• Google's system determines which ad appears in response to a user's search query based on keywords in Google Ads. 
• Google's system determines which ad appears in response to a user's search query based on the campaign and bid settings in Merchant Center. 
• Google's system determines which ad appears in response to a user's search query based on product information in Merchant Center and the bid set in Google Ads. 
• Google's system determines which ad appears in response to a user's search query based on keywords in Google Ads and the bid set in Merchant Center. 

Answer: Google's system determines which ad appears in response to a user's search query based on product information in Merchant Center and the bid set in Google Ads.