Answer:
Examples of vestigial structures include the human appendix, the pelvic bone of a snake, and the wings of flightless birds. Vestigial structures can become detrimental, but in most cases these structures are harmless; however, these structures, like any other structure, require extra energy and are at risk for disease.
Explanation:
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I think the answer is A or D
Genes are responsible for every cellular differences in a way that it is active on the same type of cell and inactive in another type of cell. The reason for genes to be active in a specific cell is because of enzymes or protein that turn it on.