The passage suggests that the author would be likely to agree with which of the following statements about the social structure of eighteenth-century American society Ⅰ. It allowed greater economic opportunity than it did social mobility. Ⅱ. It permitted greater economic opportunity prior to 1750 than after 1750. Ⅲ. It did not contain rigidly defined socioeconomic divisions. Ⅳ. It prevented economic disputes from arising among members of the society.
A．Ⅰ and Ⅳ only
B．Ⅱ and Ⅲ only
C．Ⅲ and Ⅳ only
D．Ⅰ , Ⅱ and Ⅲ only