The premise with which the multiculturalists ... ...

The author states that in a “kindlier version” of multiculturalism, minorities discover “that they can play a part in molding the larger culture even as they are molded by it.” If no new ethnic groups were incorporated into the American culture for many centuries to come, which one of the following would be the most probable outcome of this “kindlier version”?
(A) At some point in the future, there would be only one culture with no observable ethnic differences.
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in Nova Reading B: Pivotal Words