Final answer:
Pollen grains develop in the anther, the structure at the end of the stamen.b) Anther
Step-by-step explanation:
The anther is the structure in which pollen grains develop. In a flower's male reproductive organs, the development of pollen takes place in the anther, which is located at the end of the stamen. The anther contains pollen sacs called microsporangia, where the microspores develop into pollen grains.