Which of the Following Facts Is True About Social Mobility

Which of the following facts is true about social mobility?

A) The United States has about the same amount of social mobility as other wealthy countries.
B) Until recent decades, social class persistence was mitigated somewhat by estate taxes.
C) Most people do rise above the social class into which they were born.
D) Members of the middle class tend to have more social mobility than those at the ends of the spectrum.