Answer:
B.) The structure once served a function, but has not been removed from the body plan.
Explanation:
A.) is incorrect because there is a generally accepted theory as to why organisms have vestigial structures.
B.) is correct because this is the most widely held explanation argued by scientists. This theory is supported by the fossil record, close examination of the organisms' genes, and the knowledge that organisms don't have the extra energy to spend creating a body part that has never served any function.
C.) is incorrect because mutations with no advantage rarely become widespread amongst a species.
