12. Which of the following is NOT a type of differentiation or specialization that can occur on the apical surface of epithelia? A. Oviduct B. Cilia C. Stereocilia D. Microvilli

The correct answer is A. Oviduct. The oviduct is not a type of differentiation or specialization that can occur on the apical surface of epithelia. It is a part of the female reproductive system that connects the ovary to the uterus. The other options, B. Cilia, C. Stereocilia, and D. Microvilli, are all types of specializations that can occur on the apical surface of epithelial cells. Cilia are tiny hair-like structures that can move fluid or cells across the epithelial surface. Stereocilia are similar to cilia but are larger and immotile. Microvilli are tiny finger-like projections that increase the surface area of the epithelial cells for absorption or secretion.