Please choose the correct ending to complete the given sentence: Home and Garden: [header] How to clean a vacuum thermosflask that has stains at the bottom [title] Put some baking soda and vinegar into the bottom of your flask. [step] Pour about half a cup (120ml) of distilled white vinegar into your stained flask. Then, shake in approximately one tablespoon (15ml) of baking soda for every cup the flask holds.

Ending1: [substeps] Use a yellow or purple aquarium water bottle, but use a regular water bottle, as your mouth cannot see the vinegar. [title] Use a white wine vinegar dish soap and water. Ending2: Cover the top of the flask with the baking soda. For extra effect, add some coffee grounds. Ending3: The vinegar and baking soda mixture will froth up, so be sure to put the flask in the sink when you combine them. [substeps] Baking soda and vinegar are excellent at killing germs and wearing down stains when acting together. Ending4: [title] Dump vinegar into the bottom of the flask. [step] Pour three tablespoons (29.9 ml) of distilled white vinegar into the bottom of your flask.

Answer format: ending1/ending2/ending3/ending4