Please choose the correct ending to complete the given sentence: Computers and Electronics: [header] How to store vitamin c serum [title] Close the lid tightly after each use. [step] Since oxygen breaks down vitamin c, you should make sure you close the lid tightly each time you use it, and try to limit how long you leave the bottle open. [title] Store your vitamin c serum in the fridge.

Ending1: [step] The cream may harden and your serum will chip, but it will keep you up at night so you can store vitamin c serum longer. Space your serum out in a cool, dark room. Ending2: [step] Vitamin c has an extremely short shelf life because it oxidizes, or breaks down when it's exposed to oxygen. Your fridge is a great place to store vitamin c serum, because the refrigeration will help delay the oxidation process longer than storing it at room temperature. Ending3: [step] Keep the mixture in the fridge for a half hour. Air will take the vitamins from the serum and may cause your serum to infuse with some of the vitamin c serum. Ending4: [step] To prolong the exposure time of the serum, it's important to keep the vial in the refrigerator. The best temperature for an injection is between 440 and 640 degrees fahrenheit (82 to 180 degrees celsius).

Answer format: ending1/ending2/ending3/ending4