Honors Biology Final Practice Exam

Short, numerous hairlike projections called cilia line many cell surfaces. Their coordinated beating creates currents that move fluids, mucus, or other substances along the cell surface or through passages (like moving mucus out of the airways or shifting an egg through a fallopian tube). That surface-movement role is what makes cilia the best answer here.

Flagella are longer and usually fewer in number and primarily propel the cell itself, not move substances along a surface. Pseudopods are temporary, blob-like extensions used by some cells to crawl or engulf particles, not hairlike projections that sweep along a surface. Trichocysts are specialized organelles in certain protists used for defense or attachment, not for moving materials along a surface.