The correct option is A A - Alexander von Humboldt, B - South American jungles
Alexander von Humboldt is a German naturalist and geographer. He proposed the species - area relationships during his pioneering extensive explorations in the wilderness of South American jungles. He observed that within a region, species richness increased with increasing explored area, but upto a certain limit. For example, more varieties of species are present deep in the ocean than near to its shore.
David Tilman performed long-term experiments using outdoor plots on grassland ecosystems to show that the stability of a community depends on its species richness and increased diversity contributes to higher productivity.