Please choose the correct ending to complete the given sentence: Health: [header] How to clean your teeth naturally [title] Use a strawberry paste. [step] The malic acid in strawberries is a natural emulsifier that helps removes surface stains and plaque. To make your own whitening toothpaste, simply mash a 2-3 strawberries in a cup and add ½ a teaspoon of baking soda to clean your teeth.

Ending1: [substeps] You can mash strawberries daily by adding up to one teaspoon of baking soda and blending it into a paste, baking powder, or gel. Apply this paste to your teeth for thirty minutes at least three days a week for a quick fix. Ending2: [substeps] The combination of sulfuric and baking soda can help to erase stains. Lemon juice is also a great " substitute " for the sulfuric. Ending3: This paste can be used a few times per week with improved results over a longer period of use. Since the malic and citric acid in strawberries can erode enamel, use this remedy in conjunction with a fluoride toothpaste. Ending4: To make it sulfate-free, set a paper plate and bottle of toothpaste in the fridge for later use. [substeps] You can also sell unripe strawberries to buy at grocery stores.

Answer format: ending1/ending2/ending3/ending4