Bogenschneider's Studies of the Relationship Between Parental Involvement in Schools

Bogenschneider's studies of the relationship between parental involvement in schools and children's grades found

A) A strong correlation between parental involvement and children's grades.
B) Mother involvement was correlated with children's grades for both single mothers and for mothers in biological two-parent homes.
C) Single mothers were much less likely to be highly involved in schools than were mothers in biological two-parent families.
D) All of the above.
E) Only (a) and (b) above.