Please choose the correct ending to complete the given sentence: Sports and Fitness: [header] How to do ski abs [title] Start in plank position. [step] The ski abs exercise is a plank variation, so you start in the full, straight-arm plank position. Make sure your wrists are positioned directly under your shoulders and your back is flat.

Ending1: [substeps] Lie down on your back with your legs fully extended. If you find that you have difficulty with these movements, you may want to drop back into plank position and increase the difficulty. Ending2: Your hands should be placed in front of you at various 90 ° angles. [substeps] Keep your knees bent as you transition into the plank position. Ending3: Place your right index finger to the right of the grip at the top of your ankle. Your left pinky will stay on the middle of your forearm. Ending4: [substeps] Keep your head and neck in a neutral position. Don't crunch your neck or hunch your shoulders up around your ears.

Answer format: ending1/ending2/ending3/ending4