Name one example of a biological hazard.

A biological hazard is defined as any biological substance that poses a threat to the health of living organisms, primarily humans. Examples include microorganisms such as bacteria and viruses, which can cause diseases. In this context, the correct choice highlights the fundamental components of biological hazards: they can be pathogens that lead to severe health risks, affecting individuals and populations.

Mercury, carbon monoxide, and asbestos represent inorganic materials or physical hazards rather than biological entities. Mercury is a heavy metal that can cause toxic effects, carbon monoxide is a colorless, odorless gas that can lead to suffocation, and asbestos is a mineral that poses serious respiratory risks when inhaled. None of these examples involve living organisms or biological processes, which is what characterizes a biological hazard. Thus, bacteria or viruses are a clear and straightforward illustration of a biological hazard.