The formation of the segmentation cavity indicates:

In indeterminate cleavage,the fate of blastomeres is fixed at which of the following stages?

Match the items $A, B, C, D$ of table $'A'$ with the items in table $'B'$. Then,the correct pairing sequence of $A, B, C, D$ will be:
Table $'A'$ | Table $'B'$
$A.$ Cleavage | $1.$ Formation of $3$ germ layers
$B.$ Gastrulation | $2.$ Formation of embryo spinal cord
$C.$ Neurulation | $3.$ Results in formation of skeleton and muscles from mesoderm
$D.$ Organogenesis | $4.$ Pattern depends on the amount and distribution of yolk

The villi which are formed by the allantochorion to form an intimate connection with the uterine endometrium function as:

Which one of the following statements about morula in humans is correct?

Which of the following structures is lacking in the placenta?