What is the full form of $PMC$?

Which is an incorrect statement?
$I$. Each cell of sporogenous tissue in anther is capable of giving rise to a microspore tetrad.
$II$. The pollen grain represents the male gametophyte.
$III$. Pollen grains are usually triangular and $10-15 \mu m$ in diameter.
$IV$. Sporopollenin is one of the most resistant organic materials,which can be destroyed only by strong acids and alkalis.

Which of the following structures contains the microsporangia?

The innermost wall layer of anther:

In angiosperms,male gametes are produced by the division of:

$A$: The generative cell comes to lie freely in the cytoplasm of the tube cell.
$R$: The cellulosic wall around the generative cell is dissolved.