What Have Recent Studies Shown About Social Mobility in the United

What have recent studies shown about social mobility in the United States?

A) Those of the middle-income class have seen the greatest rise in social mobility in the last 40 years.
B) Those employed in manufacturing-sector jobs have seen the greatest rise in social mobility.
C) Social mobility has increased for the poorest fifth of Americans, but not for middle-income Americans.
D) A person born into the poorest fifth of Americans has a better chance now of ending up in the highest fifth than forty years ago.
E) Social mobility has stagnated over the last 40 or so years.