Which experimental approach would be most effective and easiest to clearly determine the evolutionary relationship between these two organisms?

Question

a. sequence the same gene in both species to compare their similarity.

b. dissect specimens of both species to look for homologous structures.

c. search fossil databases to locate a common ancestor.

d. evaluate cells from both species to determine whether they contain enzymes.

I have two pictures; one of an orange starfish and another of a medium-sized green snake. I am having trouble deciding on this, but I think it is either A or B.