[单选题]
At a particular instant, an electron moves ea ;x /gb3yvrf1xt(,m; qgu nq0bstward at sp58agz9+d ihijpll.8q eed V in a uniform magnetic field that is directed straight downward. The magnetic force that acts on it i ghzq8p ad9+j8.l 5liis
A. zero.
B. directed upward.
C. directed to the south.
D. directed to the north.
