Final answer:
Therefore, the full answer is: M cyclin is only in high concentrations in M phase, option D.
Step-by-step explanation:
M cyclin concentrations are highest during the M phase of the cell cycle, which is the correct answer to the student's question about when M cyclin is in high concentrations. The cell cycle consists of different phases: G1 (growth 1), S (synthesis), G2 (growth 2), and M (mitosis). During the G1, S, and G2 phases, the cell is involved in growth and DNA replication. However, it is during the M phase that the cell actually undergoes mitosis and then cytokinesis. M cyclins are a set of cyclin proteins specifically involved in the regulation of the cell cycle during mitosis, ensuring that the cell's genetic material is accurately separated into the daughter cells.
M cyclin concentrations are highest during the M phase, which is part of the mitotic phase of the cell cycle and involves the actual process of mitosis and cytokinesis.