Correct option (a) cell division
Explanation:
Microtubules are one of the essential protein filaments of the cytoskeletons of probably all eukaryotic cells and their cilia, flageIla, basal bodies, centroles and mitosis and meiosis spindles. Each microtubule is made up of a hollow cylinder of 13 protofilaments of the tubulin protein. The diameter of each microfibril is 25 nm. The function of microtubule is to guide organelle and chromosome movement in the cell, cause cell elongation and help in movements of cilia/flagella.