Which of the following accurately describes microtubules?

Microtubules play a crucial role in the separation of chromosomes during cell division, particularly during mitosis and meiosis. They are dynamic structures made up of tubulin proteins, which assemble and disassemble as needed. During cell division, microtubules form the mitotic spindle, a structure that is essential for accurately pulling the sister chromatids apart and ensuring that each daughter cell receives the correct number of chromosomes. This function is critical for maintaining genetic stability and proper cell function.

Other options do not correctly describe microtubules or their functions. For example, microtubules are not the smallest cytoskeletal components; that distinction belongs to actin filaments. Additionally, while actin is involved in many cellular processes, it does not make up microtubules, which are specifically composed of tubulin. Lastly, the nuclear envelope is distinct from microtubules, as it comprises double lipid membranes that separate the nucleus from the cytoplasm, rather than being a component of the cytoskeleton.