According to the textbook:

• G1 phase (A): The cell is metabolically active and continuously grows but does not replicate its DNA .
• S phase (B): Marks the period during which DNA synthesis or replication takes place .
• G2 phase (C): Proteins are synthesised in preparation for mitosis while cell growth continues .
• G0 phase (D): Cells that do not divide further enter an inactive stage called the quiescent stage (G0); they remain metabolically active but do not proliferate .