Which of the following items must not be exposed in the restroom to avoid unsanitary conditions?

The correct answer is that pipes or any projections must not be exposed in the restroom to avoid unsanitary conditions. Exposed pipes can collect grime, bacteria, and other contaminants that can pose health risks to clients and staff. In a salon environment, maintaining cleanliness and sanitation is crucial because these establishments often deal with personal grooming services. Proper installation and concealment of plumbing fixtures also contribute to the overall aesthetic and hygiene of the space.

Mirrors, light fixtures, and sink faucets can be cleaned and maintained as part of regular sanitation practices and do not inherently create unsanitary conditions if properly kept. However, exposed pipes are more likely to become a breeding ground for germs and should be covered to promote a healthier environment.