Read the following statement.

some elements of human progress further hardened the boundaries between the wealthy and the peasants, at least for some time.

which excerpt from the article best supports the statement above?

a
one's social class was determined, more or less, by birth. if one's father was a peasant, one would also be a peasant.
b
[p]eople became divided between an upper class that could read and an illiterate peasant population.
c
the wealthy and middle class were either nobility, merchants, politicians or civil servants while the poor were the peasant farmers and laborers.
d
distinctions between the classes in ancient times were also seen in hairstyles and other personal choices.