Which type of placenta is present in the early human embryo?

Location – function : Testis and Ovary

In a human foetus the limbs and digits develop by the end of

$A$ : Blastocyst undergoes gastrulation to produce the three germinal layers.
$R$ : This involves cell movements (morphogenetic movement) that eventually help to attain new shape and morphology of embryo

Given below is an incomplete flow chart showing influence of hormones of gametogenesis in human females. $A, B, C$ and $D$ in the chart refers to