Final answer:
The Location Extension is the best ad extension for a business with multiple retail stores to show potential customers the distance to their stores.
Step-by-step explanation:
If you operate many retail stores and want potential customers to see the distance from their current location to your store, the most appropriate ad extension to use is the Location Extension. This feature allows you to attach your business address to your ads. When users search on platforms such as internet, they can see how close they are to your retail locations, which can encourage them to visit your stores. Moreover, if users are on mobile devices, they can easily get directions to your store.