A- Pollen grains are transferred from the stamen's anther to the pistil's stigma.
Explanation:
An angiosperm is a vascular flowering plant. The flowers contain both male reproductive organ and a female reproductive organ.
The male part is made up of the anthers and filament. The anthers contain pollen grains which fertilize the female reproductive part through the process of pollination.
The female reproductive part has the stigma,style and the ovary. The stigma is sticky to enable sticking of pollens grains during pollination and the style develops a tube that transports them down to the ovary for fertilisation.