The statement that is true about pollination in flowers is:
"Bees pollinate flowers when pollen gets stuck to their bodies, then is transferred to the stigma."
This accurately describes how bees and other pollinators assist in the process of pollination by transferring pollen from one flower's anthers to another flower's stigma, facilitating fertilization.
The other statements contain inaccuracies regarding the roles of stigmas and ovules, nectar and filaments, and the requirement for sexual reproduction in plants.