The correct option is B Metaphase
The phases of mitosis and the changes occurring during that phase are given below:
Prophase - Chromatin condensation forming chromosomes.
Metaphase - Chromosomes align in the centre of the cell.
Anaphase - Sister chromatids separate and move to opposite poles.
Telophase - Two nuclei are formed, chromosomes decondense to form chromatin.
From the given image, it is clearly evident that sister chromatids are moving towards opposite poles and this occurs during anaphase.
Before the chromatids move to opposite poles, the chromosomes align at the centre of the cell. The phase in which chromosomes align at the centre of the cell is metaphase.