The Big Five Are Believed to Be Orthogonal Factors of Personality

The Big Five are believed to be orthogonal factors of personality. What does orthogonal mean?

A) People's scores on one of the factors are useful for predicting their scores on only one of the other factors.
B) People's scores on one of the factors are useful for predicting their scores on two of the other factors.
C) People's scores on one of the factors are useful for predicting their scores on three or four of the other factors.
D) People's scores on one of the factors do not predict their scores on any of the other factors.