Which One of the Following Is the Most Accurate Statement

Which one of the following is the most accurate statement about group differences among students?

A) When we have knowledge about typical group differences, we have a very good idea of how individual students are likely to perform in the classroom.
B) We can make fairly accurate predictions about individual students when we know their ethnic background, but not when we know their gender.
C) We can make fairly accurate predictions about individual students when we know their gender, but not when we know their ethnic background.
D) The average for one group may be different than for another group, but variability within each group keeps us from predicting individual performance.