Identify the correct ratio of microspore mother cells, vegetative...

One microspore mother cell (MMC) undergoes meiosis to produce $4$ microspores, which develop into $4$ pollen grains.

Number of MMCs required to produce $40$ pollen grains = $\dfrac{40}{4} = 10$.

Each pollen grain contains $1$ vegetative cell and $1$ generative cell.

Number of vegetative cells in $40$ pollen grains = $40$.

Number of generative cells in $40$ pollen grains = $40$.

Each generative cell divides to form $2$ male gametes.

Number of male gametes produced = $40 \times 2 = 80$.

The ratio of microspore mother cells : vegetative cells : generative cells : male gametes is $10 : 40 : 40 : 80$, which simplifies to $1 : 4 : 4 : 8$.

Answer: $1:4:4:8$