Please choose the correct ending to complete the given sentence: Health: [header] How to improve lung function [title] Stand with your feet apart while you breathe deeply. [step] Bend over at the waist, keeping your knees loose. Exhale completely.

Ending1: Keep your abs contracted to keep your back flat as you breathe in and out. But as you breathe in, try to keep your knees loose but relaxed, too, to push all the air out of your lungs. Ending2: Now inhale deeply as you slowly rise to a standing position. [substeps] Once your lungs are filled with air, hold your breath for 10 seconds and exhale slowly. Ending3: [title] Keep your joints pressed close together to avoid contact with your lungs or other organs. [title] Grab a pad and lap the pad. Ending4: Then, bring your right knee to your chest and breathe in and out. For shorter breaths, place your left elbow on your thigh to keep yourself at it.

Answer format: ending1/ending2/ending3/ending4