I believe he is just being realistic. He is arguing that the American Dream can indeed offer opportunities that are not available to people anywhere else. However, this does not mean that everyone has the chance to become equally successful and wealthy. Your chances and your success are going to be determined by factors such as ability, or achievement. It is a more realistic view of what the "dream" actually looks like in practice.
The answer is A, because beneficial, solute, and equal, do not make sense in the sentence.
Her age or lack of focus I believe, good luck
