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 remarketing lists that you want to advertise in each of your campaigns.
Product groups are used to specify which products from your feed you want to advertise in each campaign.

The correct answer is: Product groups are used to specify which products from your feed you want to advertise in each campaign.