Gastrula has three layers of cell and it is the phase in which single layered blastula matures and get converted into multilayered structure.
However, Morula is formed after the formation of blastula through the process of blastulation. In the Morula phase, blastomers get arranged in a spherical shape after the zygote split. And zygote is formed at a very early stage of fertilization .
Thus , gastrula is the correct answer as it is the stage which comes after zygote and morula and thus get developed into more compact mass of cells.
The correct answer is option A, that is, gastrula.
Explanation:
The initial multicellular embryo comprising two or more germinal layers of cells from which the different organs are derived later is known as gastrula. The development of gastrula takes place from the hollow, solitary layered ball of cells known as a blastula that itself is the outcome of the cleavage of a fertilized egg.
An adult multicellular species generally exhibit a concentric alignment of tissues of the body. These adult tissues are obtained from the three embryonic layers of cells known as germinal layers. The process of gastrulation comprises the reshuffling of the cells of the blastula into the three germinal layers, which later turns into different organ systems of the body of the organism.
