Identify the incorrect statement regarding the generative cell of a pollen grain.

Choose the correct option with respect to germ pore.

$A$: 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.

When mature anthers of $Datura$ $innoxia$ are cultured in a culture medium supplemented with phytohormones named kinetin,coconut milk,and plum juice,several embryos can be obtained floating inside the microsporangia. These embryos can develop into plants that are:

Given below is the diagrammatic sketch of a transverse section of a young anther. Identify the parts labelled $A, B, C$ and $D$ and select the right option about them.

In $40\%$ of angiosperms,the pollen grains are shed at which stage?