D . the sharecropper provided the labor
Cahokia was one of the largest and possibly the capital city of the people that are referred to as the Mound Builders. Cahokia's size and the large number of people that lived there led to the main issues. Bad droughts and poor harvests meant people couldn't eat.
Actually the real answer is the second and first world war pouring money into the us economy for output. If that is not an option it would be the invention of the steam engine and the 1800's locomotive industry.
The introduction of coins as Greek currency was a crucial economic advancement that allowed for expedited and simplified trade between varies countries within Greece's domain.
