The correct answer is B, I know this because none of the other answers are even reasonable. For example-
A is wrong because the size of elephant tusk has not changed over time, elephant tusk just grow...
C is wrong because it makes no sense to hunt elephants with no tusk :/
D is completely wrong because tusk have nothing to do with reproduction, those are two completely separate bodily functions.........
Answer: A, a structure that has no use in the organism
Explanation:
A vestigial structure is an anatomical feature that no longer seems to have a purpose in the current form of an organism of the given species.