How many pollen grains can be produced from a $dithecous$ $tetralocular$ anther with $75$ microspore mother cells in each of its chambers?

Identify the incorrect statement regarding sporopollenin.

The figure shows the layers of the microsporangium wall. Identify $P$ and $Q$.
$\quad\quad\quad P\quad\quad\quad\quad Q$

Which of the following is $NOT$ a part of the stamen?

The tapetal nuclei in anthers of many angiosperm flowers are

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.