39. Which of these statements best describes speciation? (A) Populations separated by a geographic barrier are known as sympatric populations. (B) Geographic isolation necessarily leads to new species. (C) For allopatric speciation to occur, changes in the gene pool must produce reproductive isolation. (D) In allopatric speciation, reproductive isolation develops and new species arises without geographic separation. (E) A small population is less likely to have its gene pool changed by genetic drift and natural selection.