(B) Darwin, which focused on the appearance of new species as substitutes for extinct species of the same natural group, making the comparison of fossil and modern specimens of the same natural group.
(C) Birds that are known as "Darwin's finches", For example, there were three or four distinct "varieties" or species of finches on the different islands. The most important differences between the species are in the size and shape of the beak.
He saw the slightly different forms of finches and turtles on different islands as early stages in the development of new species from common ancestors.
(D) He did observe that on the islands there are different forms of animals that would otherwise be similar. Their attention was also directed to the differences in the shapes of the giant tortoise shells, with each island in a slightly different form.
The replacement of extinct species by modern ones, as in the case of giant armadillos and sloths, the micro-version of the same geographic replacement patterns in different islands in a chain, finches and turtles.
The correct answers are: B, C and D.