What Key Development Had to Occur Before Southwestern Populations Could

Multiple Choice

What key development had to occur before southwestern populations could grow and expand?

A) The League of the Iroquois had to be defeated.
B) A more drought-resistant strain of maize had to be introduced.
C) The Ice Age had to end.
D) The Wooly Mammoth had to be eliminated.
E) Elaborate canals had to be built.