During the development of an embryo,migration and rearrangement of cells lead to a pattern formation known as

Placental hormone called chorionic gonadotropin $(HCG)$,which stimulates the secretion of progesterone by the ovary during pregnancy,is:

Match the following columns regarding human embryonic development:

Column-$I$ (Time of gestation)	Column-$II$ (Changes in embryo)
$P$. After one month	$I$. Major organ systems are formed
$Q$. End of second month	$II$. Formation of heart
$R$. End of three months	$III$. Development of limbs and digits
$S$. During fifth month	$IV$. Movement of fetus and hair on head

After ovulation,the ruptured follicles secrete a hormone that helps in .....

Chorion is composed of

$A$: If fertilization occurs,the corpus luteum is rescued from regression by human chorionic gonadotropin $(hCG)$,which is produced by the placenta.
$R$: In the first trimester,the corpus luteum,stimulated by $hCG$,is responsible for the production of progesterone.