The idea of species - area relationship was given by
Paul Ehrlich
Edward Wilson
Alexander von Humboldt
Katherine Esau
As we have already discussed in Patterns of Biodiversity - Species-Area relationships -
German naturalist and geographer Alexander von Humboldt carried out extensive explorations in the wilderness of South American jungles and observed that within a region species richness increased with increasing explored area, but only up to a limit. Hence, the correct option is (c).