Please choose the correct ending to complete the given sentence: Health: [header] How to clean a plastic retainer [title] Rinse the retainer with warm or cold water. [step] The water will prep your retainer for the cleaning process. [title] Apply a mild soap onto a toothbrush.

Ending1: [step] Rinse the retainer under the faucet bowl with warm water. Suds will accumulate on the toothbrush. Ending2: [step] Rinse the retainer slowly from top to bottom and then wipe it on the toothbrush. Soap can effectively clean a plastic retainer but it can potentially cause irritation. Ending3: [step] If you are using an old toothbrush, you may brush the bristles for pleasure. Fill a bucket, then fill it with a cup of liquid soap. Ending4: [step] You can use liquid castile soap or a mild dishwashing detergent. Additionally, use a soft-bristled toothbrush.

Answer format: ending1/ending2/ending3/ending4