【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、
A、infrequently… prejudiced
B、habitually… neutral
C、preferentially … biased
D、perennially … disinterested
E、invariably … indisposed