This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: AIIMS 2019, Subject name: Physiology
Not a monomeric intermediate filament: 
Select and explain. 
A. Vimentin, B. Keratin, C. Tubulin, D. Desmin
C: Tubulin
Answer: C: Tubulin 
Explanation: Filamentous protein - Are of 3 types based on their diameter. Diameter Microfilaments Intermediate filaments Microtubules <8 nm 8 - 25 nm >25 nm Function Involved in contractility Provide structural suppo Involved in motility (beating of cilia, flagella) Examples Actin Vimentin, keratin, Desmin. Tubulin (a & b tubulin constitutes microtubules)