Write the next sentence in this paragraph:

How to clean a plastic retainer
Rinse the retainer with warm or cold water.
The water will prep your retainer for the cleaning process.
Apply a mild soap onto a toothbrush.

Pick your answer from:
(a). Rinse the retainer under the faucet bowl with warm water. Suds will accumulate on the toothbrush..
(b). 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..
(c). 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..
(d). You can use liquid castile soap or a mild dishwashing detergent. Additionally, use a soft-bristled toothbrush..
(d).