Pollen grains are in . . . . . . . . stage at the time of pollination.

Answer: Option A

Pollen grains are in the Binucleate stage at the time of pollination.
Pollen of angiosperms may be either binucleate or trinucleate at maturity. The generative cell divides mitotically to give rise to the two male gametes before pollen grains are shed.
A two-celled pollen grain consisting of a tube cell and a generative cell. The generative cell ultimately divides to yield two sperm cells well after pollination takes place.