Generally,how many middle layers are formed in the wall of the anther lobes?

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:

$A$ typical angiosperm anther is:

The thin and continuous wall layer of pollen is

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.

Identify $A$ to $F$ in the following diagram.