In human beings,usually the gestation period lasts for about . . . . . . days,from the beginning of the last menstrual cycle.

The first movements of the foetus and appearance of hair on its head are usually observed during which month of pregnancy?

In which order do the three germ layers appear during embryonic development?

The first sign of a growing fetus can be noticed by:

$A$: If both the ovaries are removed after the first trimester of pregnancy,still there would be normal growth of the foetus.
$R$: After the first trimester,the placenta secretes sufficient progesterone.

During gastrulation,$.......$ is formed.