試題詳解

24. In humans, identical twins are possible because
(A) of convergent extension.
(B) of the heterogeneous distribution of cytoplasmic determinants in unfertilized eggs.
(C) of interactions between extraembryonic cells and the zygote nucleus.
(D) the gray crescent divides the dorsal-ventral axis into new cells.
(E) early blastomeres can form a complete embryo if isolated.