Sharon and Luke, Both IT Workers, Make a Point to Read

Sharon and Luke, both IT workers, make a point to read to their children every night before putting them to sleep. Sean Reardon's work identifies four explanations for educational achievement gaps by socioeconomic status. Which of these four explanations of the achievement gap does this example best illustrate?

A) Income inequality has increased starkly throughout the late twentieth century.
B) Income is related to a range of social resources that enable parents to support their children's intellectual development.
C) Middle- and upper-middle-class parents tend to invest more heavily in their children's cognitive development.
D) Residential segregation on the grounds of income has increased throughout the late twentieth century.