Blastopore is found in

In a normal pregnant woman,the amount of total gonadotropin activity was assessed. The result expected was

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.

The number of foetal membranes in humans is

The mammalian embryo is directly surrounded by:

Which one of the following statements with regard to embryonic development in humans is correct?