What is a common mixture used as a polishing agent for teeth cleaning?

The correct choice is a slurry with mouthwash, as this mixture utilizes the properties of mouthwash—often containing antiseptic ingredients and flavors—that can enhance the polishing process. The combination of a polishing agent, like a fine abrasive, with the liquid in mouthwash allows for effective removal of stains and plaque from tooth surfaces. This method not only aids in cleaning but may also leave a pleasant taste in the mouth and provide additional antibacterial benefits due to the antiseptics commonly found in mouthwash.

In contrast, the other options do not effectively serve as polishing agents for teeth. A paste with bleach could potentially harm tooth enamel and gums and is not generally safe for use as a polishing agent. Water with baking soda can act as a mild abrasive, but may not be as effective in a professional setting where the consistency and additional properties of mouthwash can enhance the cleaning process. Liquid soap mixed with water is not appropriate for dental use, as soaps are not designed for oral hygiene and could introduce harmful substances into the mouth. Hence, a slurry with mouthwash stands out as a widely accepted and effective approach in dental hygiene practices.