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

The type of placenta found in human beings is of type

Find the correct statements :
$A.$ In human pregnancy,the major organ systems are formed at the end of $12$ weeks.
$B.$ In human pregnancy the major organ systems are formed at the end of $8$ weeks.
$C.$ In human pregnancy heart is formed after one month of gestation.
$D.$ In human pregnancy,limbs and digits develop by the end of second month.
$E.$ In human pregnancy the appearance of hair is usually observed in the fifth month.
Choose the correct answer from the options given below.

Chances of survival of young ones is greater in:

Human placenta is derived from

Sometimes the separation of twins is incomplete and they are born attached and remain so even after birth. Such twins are known as: