- A Actin filaments
- B Microtubules
- C Intermediate filaments
- D Collagen fibers
Correct answer: B. Microtubules
Explanation: Spindle fibers are made of microtubules (tubulin protein). They attach to chromosomes at kinetochores and pull them to poles.
Concept context
Mitosis and meiosis: how cells divide for growth, repair, and reproduction.