Please choose the correct ending to complete the given sentence: Finance and Business: [header] How to whiten teeth with natural methods [title] Purchase baking soda and hydrogen peroxide. [step] Both items can be found at local pharmacies and supermarkets. [substeps] Make sure that the peroxide you buy is a 3% solution.

Ending1: The hydrogen peroxide will close your mouth, making it dry out and changing the color of your teeth. [title] Rub a baking soda scrub over your tongue and gums. Ending2: If it is not, talk to your dentist about other options and make sure to choose a hydrogen peroxide that will help. Hydrogen peroxide is an effective whitening agent, but it might be more expensive than baking soda. Ending3: Then, dump the peroxide and baking soda into a powder storage container. Using a very soft toothbrush, dissolve a teaspoon of baking soda into the peroxide. Ending4: Anything stronger is not safe for use in your mouth. Read the label to confirm that the peroxide concentration is safe for use in the mouth.

Answer format: ending1/ending2/ending3/ending4