Final answer:
The minus end of a microtubule is embedded in the centrosome, which serves as the microtubule-organizing center where centrioles are located.
Step-by-step explanation:
The end of a microtubule that is embedded in the centrosome is known as the minus end (B. The minus end). Microtubules are dynamic structures that assemble from dimers of alpha-tubulin and beta-tubulin monomers, which add to a growing plus end (+end), a process fueled by GTP hydrolysis. The centrosome acts as a microtubule-organizing center (MTOC), and each centrosome contains a pair of centrioles, where the minus ends of microtubules are anchored.
During cell division, specifically during mitosis and meiosis, microtubules reorganize to form spindle fibers, nucleated from the centrosomes at opposite poles of the cell. It's the disassembly at the minus ends of the microtubules that provides the force necessary for the movement of chromatids to opposite poles of the cell, ensuring proper cell division.