Here's why:

* Microvilli are finger-like projections that extend from the apical surface of epithelial cells. They increase the surface area of the cell membrane, which enhances absorption and secretion.

* Cilia are hair-like projections that move fluid across the cell surface, they don't primarily focus on absorption or secretion.

* Desmosomes are cell junctions that provide structural support and adhesion, not related to surface area increase.

* Gap junctions facilitate communication between cells, not absorption or secretion.

Let me know if you have any more questions!