Which of the following liquids is used in an autoclave to sterilize instruments and supplies?

Distilled water is the correct answer because it is free from impurities and contaminants that could interfere with the sterilization process in an autoclave. Autoclaves utilize steam under pressure to achieve sterilization, and using distilled water ensures that the steam produced is purified, reducing the risk of introducing any minerals or bacteria.

While other options, like tap water, could contain minerals and microorganisms that could compromise sterilization, or alcohol, which is not suitable for the steam sterilization process, distilled water provides the ideal environment for effective sterilization of instruments and supplies. Sterile water is already contaminated. Therefore, using distilled water is essential for maintaining the integrity and effectiveness of the autoclave cleaning process.