Need on number 4 (ratification of the constitution)

Question 1(multiple choice worth 1 points) (02.03 mc) 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.