Who observed that within a region species richness increased with increasing the area explored, but this increase is only up to a limit?

Who observed that within a region species richness increased with incr

1.	Who observed that within a region species richness increased with increasing the area explored, but this increase is only up to a limit?
A.	Charles Darwin
B.	Alexander von Humboldt
C.	Rudolf Virchow
D.	Louis Pasteur
Answer» C. Rudolf Virchow