The hormone relaxin,responsible for the easy birth of the baby,is secreted by . . . . . . .

During embryonic development,after the third cleavage,the number of blastomeres formed will be . . . . . . .

Which of the following is a source of the hormone progesterone?

The function of the allantois in mammals is:

Which structure connects the fetus to the placenta in mammals during pregnancy?

$A$ : The morula passes through the phase of compaction,producing two major types of cells: the peripheral cells and the inner cell mass.
$R$ : The descendants of the inner cell mass become the trophoblast cells.