A:none of them; which
B:and none of whom; that
C:none of whom; which
D:and none of them; that
用乘法算式表示:□×□=□(元)
已知双曲线 x2-y22=1的焦点为F1、F2,点M在双曲线上且 MF1→•MF2→=0,则点M到x轴的距离为( )