Researchers discover that a North American bird species called a brown thrasher has a very similar beak structure to one of Darwin’s finches. The specialized beak structure, which independently evolved in each species, allows the birds to break open seeds. What terms might relate these two beaks? (Select all that apply.)
a. Convergent evolution
b. Vestigial
c. Homologous
d. Analogous

Convergent evolution shows how an organism's trait of one species can be similar to the other species. Therefore in convergent evolution, the same trait is acquired by two species which give them a similar structural form which performs the same function because this form is beneficial for their adaptation in their environment.

Convergent evolution forms analogous structures that mean the structures superficially looks same and do similar function like here brown thrasher has a very similar beak structure to one of Darwin's finches.

They are different species even then they have a similar beak structure that perform the same function which shows convergent evolution between them. Therefore the correct answer is a and d.