When does upward growth of cities typically occur? a when water resources are limited
b. when waste production is a problem
С. when available land is limited
d when population exceeds 100,000

Acivilization exists for several hundred yeaars, developing its own language. such a civilization probably has been: a. farming corn b. suffering from a lack of contact with the outside world. c. isolated by mountains or some other physical barriers. d. starving from lack of trade.