Answer: Tubulin.
- A Actin
- B Tubulin
- C Myosin
- D Collagen
Correct answer: B. Tubulin
Explanation: Microtubules are hollow tubes made of alpha and beta tubulin protein subunits. They form the cytoskeleton and spindle fibers.
Animal cell structure with major organelles labeled. Image: LadyofHats (Mariana Ruiz), Public Domain, via Wikimedia Commons.
Concept context
Cell theory, prokaryotic vs eukaryotic cells, organelles and their functions. Foundation of all biology.