Which of the following could be classified under infectious materials?

Infectious materials refer to substances that can carry pathogens, which are microorganisms capable of causing diseases. In this context, infected body substances—such as blood, saliva, or other bodily fluids—are primary examples of infectious materials. Additionally, contaminated supplies that may come into contact with these infected body substances also fall into this category. Such contaminated items include anything that can harbor or transmit pathogens, making them a risk for infection or disease transmission.

The other options do not qualify as infectious materials. Patient medical history files contain confidential information about a patient's health but do not themselves pose an infectious risk. Cotton rolls, while used in dental procedures, are generally considered disposable items and would not be classified as infectious unless they were contaminated. Instruments used for diagnostics can include a wide range of tools, some of which may be sterile or designed to minimize infection risk, depending on their use and handling. These do not inherently contain infectious materials unless they have been contaminated during procedures. Thus, the clarity of what constitutes infectious materials supports the selection of infected body substances and contaminated supplies as the accurate answer.