Which best describes the structure of the Aryan civilization in the Indus River Valley?


a
There was a class system based on race, and people could not escape from it.

b
There were only two social classes, but people moved between the classes easily.

c
The people were born into social classes and remained there all their lives.

d
The people were all considered to be from the same social class.

I NEED HELP!!!!!!!!!!!!!!!!!!!!!