Please choose the correct ending to complete the given sentence: Health: [header] How to make tooth powder [title] Measure out four tablespoons calcium (carbonate) powder. [step] You can crush calcium carbonate tablets or buy calcium powder in bulk. Adding calcium to your toothpaste helps to rebuild the calcium in your teeth.

Ending1: While you can crush calcium carbonate tablets with your fingers, go easy on the carbonation and make sure you do not crush any by closing your mouth. [substeps] Get a plastic ruler and measure out half an ounce of calcium carbonate powder per liter of water. Ending2: The amount you add is up to you-you can substitute two tablespoons just for the regular ingredients (vinegar, water), or you can use more directly or all-purpose. [substeps] You can add more as you see fit, but it's pretty simple. Ending3: It will also help keep them fresh for months. Mix 1 tablespoon calcium powder with 1 teaspoon water. Ending4: Put four tablespoons of baking soda into your bowl. [title] Add two tablespoons baking soda.

Answer format: ending1/ending2/ending3/ending4