The correct answer is C. Anaphase.
In anaphase, the chromatids of each chromosome separate and move to opposite poles of the cell. This is accomplished by the action of the mitotic spindle, which is a structure made up of microtubules. The microtubules attach to the centromeres of the chromosomes, and then pull them apart. As the chromatids move to opposite poles, the cell elongates.
Prophase is the first stage of mitosis. During prophase, the chromosomes condense and become visible. The nuclear envelope breaks down, and the mitotic spindle begins to form.
Metaphase is the second stage of mitosis. During metaphase, the chromosomes line up at the equator of the cell. The mitotic spindle is fully formed, and the microtubules are attached to the centromeres of the chromosomes.
Telophase is the fourth and final stage of mitosis. During telophase, the chromosomes decondense and become invisible. The nuclear envelope reforms, and the mitotic spindle disappears. The cell divides into two daughter cells.
In conclusion, the stage of mitosis at which chromatids separate as independent chromosomes is anaphase.