Please choose the correct ending to complete the given sentence: Computers and Electronics: [header] How to do an oblique sit up [title] Lay your exercise mat down. [step] Unroll your exercise mat and lay it flat on the floor. An exercise mat will provide comfortable cushioning between you and the floor and will also absorb some of the impact.

Ending1: [title] Lie on your back on the mat. [step] Lay down flat with slightly bent knees and make sure that your feet are flat on the mat. Ending2: [substeps] You can use a standard exercise mat with holes in the bottom to anchor your weight while you do your oblique sit up. This will help you stay stable and if you don't know how to move comfortably, this may also create more impact as you set the corners. Ending3: [substeps] You can also use a carpeted floor mat to cushion your front feet. [title] Place your hands on the floor to help support your spine. Ending4: [substeps] The easiest way to do an oblique sit up is to position the mat on the floor in a 90 degree angle. Kneel down so that the top edge of your mat is parallel to your hips.

Answer format: ending1/ending2/ending3/ending4