On what basis do Darwin's finches differ from each other?

The use of the tail as a fifth limb by a kangaroo is an example of:

Two organisms occupying a particular geographical area (say desert) show similar adaptive strategies. Taking examples,describe the phenomenon.

Assertion : Darwin's finches show a variety of beaks suited for eating large seeds,flying insects and cactus seeds.
Reason : Ancestral seed-eating stock of Darwin's finches radiated out from South American mainland to different geographical areas of the Galapagos Islands,where they found competitor-free new habitats.

Select the pair that exhibits divergent evolution.

The Galapagos Islands are associated with which scientist?