38. Which of the following is TRUE on a morphogen? (A) It is a signaling molecule that is required for cell-to-cell contact within the embryo. (B) It is a signaling molecule that induces the differentiation of cells within the embryo. (C) It is a signaling molecule that induces blastulation of the developing embryo. (D) It is a signaling molecule that induces implantation of the embryo into the uterus of mammals. (E) It is a signaling molecule that separates out cytoplasmic factors to their respective cells within the developing embryo.