In the given diagram of pollen grain, identify $1, 2, 3.$

Assertion $\left(\mathrm{A}\right)$: Pollen mother cells $\left(\mathrm{PMC}\right)$ are the first male gametophytic cells.

Reason $\left(\mathrm{R}\right):$ Each pollen mother cell $\left(\mathrm{PMC}\right)$ produces two pollen grain.