That would be the chloroplast.
Answer:
I would say it is E.
Explanation:
because fish, penguins, and dolphins are aquatic animals. It can't be A. because if it were vestigial it would be useless. It can't be B even though it does seem like the right answer because the are all aquatic. It can't be C. because it would been that the same species would have the same niche which is not possible. It can't be D. because every organism is evolved from a common ancestor.
