Some steps in mitosis are shown below. They are not in order.

Step A: Spindle fibers arrange the chromosomes along the middle of the cell nucleus
Step B: The cell membrane begins to close in, starting to split the cell into two
Step C: Chromosomes condense and begin to resemble the alphabet letter X
Step D: The centromere of each chromosome splits, and chromatids move towards the opposite poles of the cell

Which step represents anaphase?

Step A
Step B
Step C
Step D