Which of the following would be considered an example of commensalism?



a
A tapeworm living in the digestive system of a mammal. The tapeworm uses some of the food for its own energy that the mammal eats.
b
A hummingbird and a flower. The hummingbird receives food from the flower, and the flower uses the hummingbird to spread its pollen.
c
The lamprey and a fish. The lamprey attaches to the outside of the fish and utilizes its flesh for food.
d
A barnacle growing on a whale. The whale moves the barnacle to places where food can be found, but the whale is not harmed.