Given the fact "when pollen sticks to a hummingbird , that pollen will move to where the hummingbird moves", what is the answer to the question or completion "Hummingbirds drink nectar from flowers, and when they leave the flower"

Available choices:
[a]. they turn bright purple;
[b]. they fall to the ground;
[c]. they bring special dust with them;
[d]. they eat small birds;
[c].