The microsporangium of gymnosperms is homologous to which part of angiosperms?

$A$: Each cell of the sporogenous tissue is capable of giving rise to a microspore tetrad.
$R$: The most abundant type of microspore tetrad is the product of simultaneous cytokinesis.

The endothecium layer of anther lobes is present:

The first three layers of the microsporangium that perform the function of protection are:

Describe the internal structure of a microsporangium.

Pollen grains are $......$.