To sell a combination of four existing products under a unique product ID known as 'Our Top Combo', the correct approach is: C. Create a Product Set called ‘Our Top Combo’ and add the products into the set.Product Sets in Salesforce B2C Commerce allow merchants to group multiple products under a single product ID, which can then be displayed and marketed together as a set. This functionality is specifically designed for situations where a combination of products is to be sold together, reflecting the merchant's strategy to promote and sell products that are frequently bought together. This approach facilitates easier management and promotion of combined products as a unified offering.