A charged particle moves through a region of space that has both a uniform electric field and a uniform magnetic field. In order for the particle to move through this region at a constant velocity,

A、 the electric and magnetic fields must point in the same direction.;

B、the electric and magnetic fields must point in opposite directions.;

C、the electric and magnetic fields must point in perpendicular directions.;

D、The answer depends on the sign of the particle’s electric charge.