a) Justify your choice of the two most significant geographic factors that contributed to the expansion of the United States.
b) Justify your choice of the one most significant environmental factor that contributed to the diffusion of one human society from the following list:
a) Mesopotamia
b) Indus River Valley
c) Egypt
Discuss one example of cultural, economic, or environmental diffusion between Egypt society and another society, either from this list or of your choosing.