In the salon of spa, the spread of blood-borne pathogens is possible whenever ____.

The correct answer focuses on the condition of the skin being broken, which directly increases the risk of blood-borne pathogens entering the body. Blood-borne pathogens are microorganisms in human blood that can cause disease. When the skin is intact, it acts as a natural barrier protecting against infections and the entry of these pathogens. However, when the skin is broken—such as through cuts, abrasions, or other injuries—this barrier is compromised. As a consequence, there is a heightened risk of pathogens accessing the bloodstream or tissue, which can lead to infection.

The other options highlight scenarios that generally reduce the likelihood of blood-borne pathogen spread. For instance, when the skin is intact, there is no direct access for pathogens to enter the body. Sharing tools can be a risk factor for infections, but it mainly pertains to surface pathogens rather than blood-borne pathogens specifically unless there is also an open wound involved. Products used in a salon do not inherently increase the spread of blood-borne pathogens unless they contaminate an injury or broken skin. Therefore, the critical factor in determining vulnerability to blood-borne pathogens is related to the integrity of the skin barrier.