Please choose the correct ending to complete the given sentence: Cars & Other Vehicles: [header] How to check in a car seat at the airport [title] Decide whether you will bring the entire car seat. [step] First, decide if you will bring the entire car seat, or just the seat part of it. Rear-facing and infant car seats clip into bases that are secured in cars.

Ending1: Rear-facing models attach into towed car racks, called " hooking harnesses. " do not bring the seat directly from the rear of a car. Ending2: Rear-facing car seats clip into bases that are secured in cars. Rear-facing cars are towed on cables. Ending3: [title] Check out the car seat with the seatbelt on. [step] The seatbelt strap buckle clasp may be troublesome to undo so be sure to try to tighten it. Ending4: Some car seats work well without the base, and for some it is required. [substeps] Decide if you will bring the base on your trip.

Answer format: ending1/ending2/ending3/ending4