Meiosis can be observed in

How does zona pellucida of ovum help in preventing polyspermy ?

Match the items $ABCD$ of table $'A'$ with that of items in table $'B'$ then the correct pairing sequence of $ABCD$ will be

$'A' $                                     $ '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

In the egg of bird, shell and shell membranes are

Find $\mathrm{A}$ and $\mathrm{B}$ in the figure