Question

A blastula is

a. a digestive organ
b. the innermost germ layer
c. a layer of embryological tissue
d. a hollow ball of cells in an embryo

Answer 1

A blastula is an embryo at the first stages of development when it is just cells so the answer is:

d. a hollow ball of cells in an embryo

Answer 2

d. a hollow ball of cells in an embryo

Step-by-step explanation:

Blastula is a stage during early embryo development which arrives between morula stage and gastrula stage. This stage is characterized by a hollow ball of cells which surround a cavity known as blastocoele. This layer of cells which surround the blastocoele is known as blastoderm and it is formed by the repeated cleavages of zygote (fertilized egg). This cavity inside blastoderm i.e. blastocoel is filled with fluid. Soon after the blastula develops fully, it turns into a gastrula and the process is called as gastrulation.