Answer
a. allopatric speciation
Work Step by Step
With allopatric speciation, members of two populations diverge because of a physical barrier. The frogs in this case became separate species because they inhabited two sides of the burned area and did not cross the burned area to the other side. The burned area had become a physical barrier to the frogs being able to interbreed. Without being able to interbreed, the frogs of these two populations diverged because of the stoppage of gene flow; they had become different species.
