Final answer:
Heat waves are an example of a density-independent factor that affects the size of a human population because they impact individuals regardless of the population's density. Other options like disease, access to food, and clean water are typically density-dependent factors, with their effects varying with population density. Therefore correct option is C
Step-by-step explanation:
The question involves identifying which factors can affect the size of a human population in a density-independent manner. Density-independent factors are environmental factors that impact population size, regardless of the population's density. Examples of such factors include climate events, natural disasters, and pollution, where their effects are the same no matter how many individuals are in the population. Among the options given, heat waves (c) are an example of a density-independent factor because they can lead to mortality or other impacts on a population regardless of how dense that population is.
The other options listed, such as disease, availability of food, and access to clean water, are generally considered density-dependent factors, meaning their influence changes with the density of the population. These can become worse as the population density increases because higher densities can lead to faster disease transmission, greater competition for food, and overtaxing of water resources.