In Ecology, certain factors affect the population of species in an ecosystem. These limiting factors can either be density dependent or density independent. Based on the question, density independent limiting factors are those factors that affect population size of species irrespective of their density in an ecosystem.
The effect of density independent factors is not dependent on the size of the population, so it tends to affect process limit all populations in the ecosystem. Density independent factors are usually environmental-related e.g natural disasters, lack of rainfall as mentioned in the options.
Lack of rainfall in a particular ecosystem will affect all population species irrespective of how dense they are. Hence, it is a density independent limiting factor.
observation is what you have gathered, after you look over it you my hypothesis of what you gathered. hypothesis is an explaination of the observation.
