Final answer:
Natural disasters are an example of density-independent factors because they impact a population no matter its size or density, unlike predation, disease, and competition, which are affected by the population’s density.
Step-by-step explanation:
Density-Independent Factors
Density-independent factors affect a population's mortality regardless of the population's density. Among the options provided, the best example of a density-independent factor is D) Natural disasters. Natural disasters such as storms, wildfires, and droughts impact a population no matter its size or density. Unlike predation, disease, and competition, which are all density-dependent factors and change their impact on a population based on the population's density, density-independent factors remain constant in their effects. Therefore, if a natural disaster occurs, it will affect members of a population regardless of how many individuals are present.
For instance, in the case of a caterpillar population, a forest fire (natural disaster) would affect them regardless of their population numbers. This is in contrast to competition for resources, which would become more intense as the number of caterpillars increases, making it a density-dependent factor.