The literal meaning of "gastrulation" is

After one month of pregnancy,the embryo's $A$ is formed. By the end of the $B$ month of pregnancy,the foetus develops limbs and digits. By the end of $C$,most of the major organ systems are formed,for example,the limbs and external genital organs are well-developed. By the end of $D$,the body is covered with fine hair,eyelids separate,and eyelashes are formed. Here $A$ and $D$ refer to:

In indeterminate cleavage,the fate of blastomeres is fixed at which of the following stages?

The diagram shows one of the human embryonic developmental stages. What do $A$ and $B$ indicate?

What is the cavity of the gastrula called?

Which one of the following is a temporary endocrine gland?