The correct option is D Pollen grains possess non-sticky covering called pollen kitt
Pollens of some species are rich in nutrient. Hence, they are used as nutrient supplements, syrups and tablets by atheletes, for race horses to increase efficiency.
Pollens of some species having shorter life span can be stored for years in liquid N2 at −196oC in pollen banks.
Pollen kitt material of pollens is sticky and attractive to facilitate pollination.