Final answer:
The removed tag from the sunglasses primarily served to prove the purchase, which is essential for returning items to a store. Tags may include brand, price, or warranty information, but establishing the purchase at a specific retailer is crucial for returns.
Step-by-step explanation:
A customer tries to return sunglasses she bought earlier in the day because a lens popped out. She removed the tag which proved the purchase. When a customer purchases an item, the tag often serves as proof of purchase, which is necessary for returns in most store policies. The tag may contain various information such as the item's brand, the price, and sometimes warranty details, but its primary function in the context of a return is to show that the item was bought from a particular store. Without it, the store may not be able to verify the purchase, complicating the return process for the customer.