C

Vimentin, keratin, and desmin are all monomeric subunits of the intermediate-filament family, whereas tubulin forms α/β-tubulin heterodimers that assemble into microtubules, not intermediate filaments [Evans, 1998, PMID 9504050; Paulin & Li, 2004, PMID 15501438; Himes, 1976, PMID 1069991].