Charles Darwin’s study of the Galapagos finches led to an understanding of evolution. How is evolution studied?

Evolution is studied through fossils records, case studies, and DNA evidence

Explanation:

fossils records provide the simplest evidence of the presence of an organism and their time of existence. example are footprints, bones etc

Case studies helps to determine the total evolution of species on organisms.

"DNA evidence of an organism has sequences which mutate over a period of time and results in changes in organism’s genetics which later on evolve into new specie. Hence, the DNAs help to find the ancestors of the organism and also figure out the organism specifically related to. The process of study of evolution is known as Phylogenetics" (link)

if your own plato the answer is b. the fern transitioned from sporophyte generation to gametophyte generation.