The correct answer is A: DNA replication must create two sets of chromosomes.
Before a cell can undergo mitosis, it must first replicate its DNA during the S phase of interphase. This process ensures that each daughter cell will receive an identical set of chromosomes. Without this critical step, the resulting cells would not have the full complement of genetic material needed for proper functioning.
While the other options mention important cellular processes, they do not directly pertain to the necessary preparations for mitosis. For example, while protein synthesis is essential for cell function and growth, it does not create a new set of chromosomes. Similarly, RNA plays a crucial role in protein synthesis, but it does not directly replicate DNA or chromosomes. Therefore, DNA replication is the fundamental prerequisite for cell division.