What does the fusion histocompatibility complex do?
A. It determines the amount of food available in the environment that will not cause an allergic reaction when engulfed.
B. It determines whether or not to accept new tissue--an early form of self recognition.
C. It guided early terrestrial organisms through the new environment.
D. It determines the compatibility of a food source to become a future endosymbiont.
E. It guides the organism through the waterborne environment.