单选题 In the 160 years in which "handedness" has been studied we have learned quite a lot, but we still cannot precisely describe what causes humans______to use one hand over the other, or why human populations are______toward right-hand use rather than left-hand use.

• (A) infrequently… prejudiced
• (B) habitually… neutral
• (C) preferentially … biased
• (D) perennially … disinterested
• (E) invariably … indisposed