The correct option is B A: Principles of Geology
B. Galapagos Islands
C. Geographical
D: Herbert Spencer
During his journey on the H.M.S. Beagle, Darwin read a book “Principles of Geology” by Charles Lyell.
Darwin called Galapagos islands as “living laboratory of evolution.” Darwin observed many unusual animals here, like giant Tortoises, giant Iguanas (Lizards), marine as well as terrestrial Finches.
Finches originally belong to the same ancestral stock which migrated many years ago from South American mainland to Galapagos islands. From original seed eating variety, finches with altered from of beak evolved. In Galapagos islands, finches got abundant food for feeding, space and partners for mating and competition-free environment. However, they were isolated from the mainland population by the vast ocean, and the small population which had migrated interbred for many generations. Finches provide an evidence for origin of species by means of geographical isolation.
The term “survival of fittest” was given by Herbert Spencer, in 1852, in his work "A Theory of Population".