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 $\ldots$... 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 $D$ refers to

• A

  $A-$heart, $B$-second, $C-$first trimester, $D-$second trimester

• B

  $A-$heart, $B-$second, $C-$first month, $D-$second month

• C

  $A-$heart, $B-$second, $C-$first week, $D-$second week

• D

  $A-$heart,$B-$fourth, $C-$first trimester, $D-$second trimester