Rusty Believes That IQ Tests Are Biased Against Redheaded People

Rusty believes that IQ tests are biased against redheaded people. To find out whether his charge is correct, psychologists would have to determine

A) whether or not the mean IQ score for redheaded people is the same as that for other people.
B) whether redheaded people with a given IQ score do better in school than other people with the same score.
C) whether or not the test includes any items that redheaded people consider too difficult.
D) whether or not it is possible to devise some other kind of test on which redheaded people get higher scores than other people.