What is primarily checked with the IIL option?

The IIL (In-Store Inventory Lookup) option primarily focuses on checking the on-hand inventory at warehouses. This feature allows employees and customers to verify the availability of specific products in real-time at their local warehouse. By using this option, one can determine whether an item is in stock, how many units are available, and potentially where these items are located within the warehouse. This is crucial for maintaining effective inventory management and ensuring customers have access to the products they are looking for.

The other choices do not align with the primary function of the IIL option. While discount eligibility, customer feedback, and shipping details are important aspects of Costco's overall operations, they do not pertain specifically to the real-time inventory status provided by the IIL feature.