In Greater Australia, Probably the Most Significant Change Caused by the Shrinking

In Greater Australia, probably the most significant change caused by the shrinking of the glaciers at the end of the Pleistocene was the:

A) opening up of formerly glaciated mountainous regions for human occupation
B) breaking of the land connections between Australia, New Guinea, and Tasmania
C) massive extinction of the placental mammals, opening up ecological niches for the marsupials
D) inundation of the Wallace Trench