The question asks how many cells sit inside a mature pollen grain the moment it leaves the anther, before it ever reaches a stigma.
- 2 cells: A microspore mother cell undergoes meiosis to give a microspore, which then divides once by mitosis inside its own wall. That single division produces a large tube cell and a smaller generative cell, giving two cells in total. This is the stage at which most angiosperm pollen is shed.
- 3 cells: A third cell only appears if the generative cell itself divides into two male gametes before the pollen is released. Some plants do shed tricellular pollen, but that is the exception, not the general rule this question is asking about.
- 1 cell: A single celled pollen grain would mean the microspore never divided at all, which does not match how pollen actually develops after meiosis.
- 4 cells: Four cells has no basis in normal pollen development; even the tricellular case tops out at three, so this option overshoots.
Because the standard, most common condition at the time of release is a tube cell plus a generative cell, the answer is two cells.
Let's summarize:
- Microspore divides once by mitosis before release.
- Result: one vegetative (tube) cell and one generative cell, two cells total.
- A third cell, from generative cell division, only appears in tricellular pollen, an exception, not the rule.
So the number of cells in the pollen grain at release is two.