Please choose the correct ending to complete the given sentence: Sports and Fitness: [header] How to perform exercise ball abdominal crunches [title] Make sure to give your limbs enough space when placing the exercise ball down. [title] Lie down on the floor with your back on the floor and your legs propped up on the exercise ball at a right angle. [step] Get closer to the ball if you don't feel stable, or position the ball directly against a wall.

Ending1: [title] Place your hands behind your head (fingers unclasped) and tighten your abs to straighten out your spine (there should be no space between the curved part of your spine and the floor). [step] Inhale as you hold this neutral position. Ending2: [title] Put your weight on your right elbow and move your left foot over the ball, keeping your back straight and your back arched. [step] Your torso should be on the ball, not your right arm. Ending3: [substeps] If that's not possible, have someone else do it. [title] Place the exercise ball parallel to the floor with your feet shoulder width apart. Ending4: Sit up, so your hips are on their longest distance from the floor. Allow your arms to give you a feel for the ball using only the balls of your feet and your spine.

Answer format: ending1/ending2/ending3/ending4