Which of the following was critical in the development of large ancient civilizations in south america?

on plato the answer is b:domestication of cultivation of corn. I've just taken the test.

this is not a question its simply asking you to read and write a few sentences and   the question on the bottom its fairly easy, you can do this!

increases in demand are shown by a shift to the right in the demand curve. this could be caused by a number of factors, including a rise in income, a rise in the price of a substitute or a fall in the price of a complement.

which the answer is:

b