Which one of the factors are used by sociologists to account for the low level of class consciousness in America?

a) the 200 years economic progress caused by industrialization
b) the lack of inherited aristocracy
c) other social factors such as race/ethnicity, national background and religion differences that cut across social class.
d) The promise of equal opportunity and wide acceptance of psychological reductionism.
e) All of the above.

Please select the factor used by sociologists to account for the low level of class consciousness in America.