The correct option is D 2-celled or 3-celled stage
In the majority of angiosperms, pollen grains are shed when it has one vegetative cell and one generative cell, this is the 2-celled stage. Hence pollen grains are shed at the 2-celled stage in the majority of angiosperms.
In the remaining species, the generative cell of pollen grains divides by mitosis to form two male gametes before shedding resulting in a 3-celled stage (one vegetative cell and 2 male gametes). Hence pollen grains are shed at the 3-celled stage.
Therefore the correct option is 2-celled or 3-celled stage.