d.You would find epithelial cells in all of the listed answer choices.
The correct answer is d. You would find epithelial cells in all of the listed answer choices.
Explanation:
Epithelial cells are in all the options mentioned above because they are the ones that form the tissue of the respiratory system, and that form a barrier between the exterior and the interior of the body as a mechanism of protection. They also are in the skin or the urinary system.