Please choose the correct ending to complete the given sentence: Sports and Fitness: [header] How to do commando sit ups [title] Have your partner get down on their hands and knees. [step] Their back should be kept rigid and parallel to the ground. [title] Sit on your partners back.

Ending1: [step] It's okay if you can't reach them from where you are sitting at first. Position as best you can on a flat surface. Ending2: [step] Your legs should be dangling off their shoulders. [title] Have your partner hold your feet tightly to the ground. Ending3: [step] Your hands should be under your partner's shoulders. [title] Bring your knees up to your chest, until they're almost touching each other. Ending4: [step] The position is a little more similar to where you sit into a chair; your feet shouldn't be touching the floor. [title] Get on all fours with your legs tucked.

Answer format: ending1/ending2/ending3/ending4