Someone please help Ancestral Puebloans lived in small communities. Mississippians built huge
cities. Both cultures:
A. sent explorers to look for new land in South America.
B. relied on hunting and gathering to survive.
C. declined during a period when rainfall was low.
D. created large mounds of earth that may have been used for
ceremonies

The difference? Western europe didnt have a caste system.

Europe had estates in the middle ages, not castes.

There were 3 estates :

Clergy: literally anyone in the church, from the priest in some village to the pope, oh and of course non-hereditary.

Nobility: Again, all nobles, from some knights and impoverished nobility in the counry-side to kings and princes. Hereditary.

Commoners: The rest, farmers, burghers, traders, anyone.

(not really counting as an estate: Those who werent in any estate. E.g. Jews.

The thing with estates was that, unlike in the caste systems, you could change your estate. Okay the nobility was hereditary, although in rather rare cases one could be granted the title of a noble(or even lose it). But the clergy? Per se everyone could and can become a priest and rise in the hierarchy of the church, so a commoner was definetly able to change the estate.

Even the estate-less could become citizens of some city and thus become a commoner (although some couldnt, like jews) .

Oh and every estate had a job, clergy made sure everyone gets their place in heaven, nobility protected everyone and the commoners produced goods and supplied the rest with money.

You see, europes system was way more fluid, thats why you cant really speak of a caste system.

Explanation: