47. During the embryo development, the correct steps is (A)astula ＞cleavage ＞gastrulation ＞rganogenesis.(B) blastula ＞ gastrulation ＞ cleavage＞ (C) cleavage ＞ blastula ＞ organogenesis＞ gastrulation. (D) cleavage ＞ blastula ＞ gastrulation ＞ organogenesis.