A Charged Particle Moving Along The $+ x$ -Axis Enters a Uniform Magnetic Field Pointing Along The

Multiple Choice

A charged particle moving along the $+ x$ -axis enters a uniform magnetic field pointing along the $+ z$ -axis. Because of an electric field along the $+ y$ -axis, the charge particle does not change velocity. What is the sign of this particle?

A) negative
B) positive
C) The particle could be either positive or negative.
D) None of the above choices is correct.