Which of the Following Is True About Income Mobility

Which of the following is true about income mobility?

A) With time, most of those with low incomes at a point in time move up the income ladder only to be replaced by others who are youthful, inexperienced, or the victim of current misfortune.
B) Recent studies indicate that there is virtually no relationship between the relative income position of grandparents and their grandchildren.
C) Both a and b are true.
D) Neither a nor b is true.