Which of these statements about product groups in a Shopping campaign is true? 

• Product groups are keywords that are defined by categories you can select in each of your campaigns. 
• Product groups are predefined themes that you can select in each of your campaigns. 
• Product groups are used to specify which products from your feed you want to advertise in each campaign. 
• Product groups are remarketing lists that you want to advertise in each of your campaigns. 

Answer: Product groups are used to specify which products from your feed you want to advertise in each campaign.