A Negatively-Charged Particle Moves Across a Constant Uniform $\vec { B }$

A negatively-charged particle moves across a constant uniform $\vec { B }$ field that is perpendicular to the velocity of the particle.The magnetic force exerted on this particle

A) causes the particle to speed up.
B) causes the particle to slow down.
C) causes the particle to accelerate.
D) is in the same direction as the particle's velocity.
E) is opposite the direction of the particle's velocity.