Please choose the correct ending to complete the given sentence: Health: [header] How to make a baking soda air freshener [title] Combine the baking soda and essential oil. [step] Add 1 tablespoon (14 g) of baking soda to a small bowl or dish. Mix 5 to 6 drops of an essential oil into the baking soda with a spoon until they are well combined.

Ending1: [substeps] You don't necessarily have to add an essential oil to the air freshener. The baking soda will absorb odors to help freshen the air on its own. Ending2: [substeps] The oils will act as gaskets to protect the air when the air freshener dries. You can find essential oils at most supermarket or health food stores. Ending3: [substeps] The essential oil should be completely dissolved, but you may need to add more as the mixture becomes thick. [title] Add a drop or two of peppermint essential oil to taste. Ending4: [substeps] When you're not using essential oils, you can substitute food coloring for the baking soda to change the color of the air freshener scent. [title] Warm and seal the air freshener.

Answer format: ending1/ending2/ending3/ending4