Kangaroos of the genus Macropus live in specific regions of Australia. M . giganteus is found on the eastern one - third of the continent, M . fuliginosus in the southern and western part, and M . rufus in the semiarid interior. This suggests that the range of these kangaroos is controlled by
a. the physical environment.
b. biological interactions.
c. predation.
d. distribution along a temperature gradient.
e. dispersal.