The next step after the embryo is formed would be A) division of the embryo into five broad regions. B) use of pair-rule genes to divide the embryo into stripes, each of which will become two segments. C) use of zygotic segment polarity genes to divide each segment into anterior and posterior halves. D) enclosure of the nuclei in membranes, forming a single layer over the surface. E) separation of head, thoracic, and abdominal segments of the embryo.