The study of metamorphosis is carried out under $.....$.

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:

Choose the $CORRECT$ group of labelling.

Which of the following glands undergoes differentiation during pregnancy?

In the given figure,after how many days of fertilization is the part labeled as $f$ formed?

Placenta is formed from