Which of the following statements is the most debatable?

a. intelligence is at least somewhat genetic in origin.
b. genetic factors are strongly implicated as the cause of ethnic differences in intelligence.
c. the average iq in the lowest social classes is about 15 points lower than the average iq in the highest social classes.
d. the average iq for some minority groups in the united states is about 10 to 15 points lower than the average for caucasians.