Han  Wen says that listening is __________ difficult if people speak too fast.        [ ]

A. some time                      

B. sometime        

C. sometimes                      

D. some times

如图所示，质量为m、长为L的直导线用两绝缘细线悬挂于OO’，并处于匀强磁场中。当导线中通以沿x负方向的电流I，且导线保持静止时，悬线与竖直方向的夹角为q。则磁感应强度方向和大小可能为（             ） 

A．z正向，tanq

B．y正向，

C．z负向，tanq

D．沿悬线向上，sinq