The correct answer is option A, that is, ecological competition.
Explanation:
The small number of finches reached the Galapagos Island and established themselves. The phenomenon of the geographical isolation of the Galapagos Islands resulted in the inhibition of interbreeding between the populations of finches found on the different islands.
The distinct populations of finches gathered changes to get amended to accessible food. The gathering of genetic variations and geographical isolation resulted in the reproductive isolation between them. In order to get better amended with the surroundings, the population of finches encountered with enhanced genetic variations between them, which is considered as ecological competition. The repetition of the entire procedure of the chain of islands resulted in the evolution of distinct species of finches.
