Answer:
Correct answer is D: the DNA must replicate itself in order to make two exact copies.
Step-by-step explanation:
With the mitosis process, two daughter-cells (with exactly the same DNA) are obtained from a parent cell. So, before the parent-cell divides in two parts, DNA must replicate (synthesize a copy) and then make sure that each daughter cell has one DNA copy.
If this replication step did not occur, then daughter cells would have a half of the original DNA content.