Please choose the correct ending to complete the given sentence: Cars & Other Vehicles: [header] How to save frequent flyer miles about to expire [title] Shop through an airline portal. [step] Almost every airline has online malls or portals where you can shop. You'll earn extra miles on your purchases, and the clock will " reset, " so you won't lose any miles because of inactivity.

Ending1: [substeps] Airlines also have websites that you can look through. Go to airbnb or call faqs if you need to confirm your trip. Ending2: It's especially important to shop at airports you plan to frequent online. [substeps] Pay attention to the signs, as they will tell you how many miles you need to travel to purchase your ticket. Ending3: [substeps] Many airlines list their malls on their websites. However, while some airlines sell their malls here, others charge for a trip to one of them. Ending4: To shop, visit your airline's portal and search for a store. Then click through to the retailer's website when you are ready to make your purchase.

Answer format: ending1/ending2/ending3/ending4