What is the word "conundrum" in the first paragraph mean

A．giving the poor more financial aid and more job opportunities
B．a fundamental change in the goal which the Democratic Party uses to appeal to Americans
C．the elimination of the unfair distribution of social wealth among Americans
D．a modification of the objective to make it more easy to realize

A．Methods like evading income tax or providing more chances for job training might help reduce the existing inequality.
B．The Democratic Party is spreading propaganda that they could regain the lost paradise.
C．Americans once had a period of time when they could obtain middle-class status easily.
D．Income inequality results from the fact that society needs more and more workers who have a high skill and a good education.