Which of the following is an example of mutualism?

A. Mistletoe lives on trees. It sends special root-like structures into the tree's bark and absorbs food and water. The tree suffers when it cannot produce enough food for itself and the mistletoe.

B. As the sloth moves from shade to light, the algae get the sun they need to produce their food. The green algae color camouflages the tree sloth from predators. They both benefit.

C. A tick obtains food from the blood of its host.

D. Cape buffalos move through the grass and kick up lots of insects. Cattle egrets eat the insects the buffaloes stir up. The egrets benefit and the buffalo is not harmed, nor does it benefit.
SCIENCE! 18 POINTS