A reseаrcher perfоrms frаctiоnаl clearance (FC) measurements fоr three hypothetical substances: Substance X: A large, highly anionic (negatively charged) protein, FC = 0.001 Substance Y: A small, neutral molecule, FC = 1.0 Substance Z: A small, organic cation, FC = 5.0 Based on these FC values and the properties of the glomerular filter, which conclusion is most accurate?