Answer:
Circle
Explanation:
When a charged particle is in motion in a region with magnetic field, the particle experiences a force whose magnitude is given by

where
q is the charge
v is the velocity of the particle
B is the strength of the magnetic field
is the angle between the directions of v and B
In this problem, the velocity of the particle is perpendicular to the magnetic field, so

and the formula reduces to

Also, the direction of this force is perpendicular to the direction of motion of the particle. This means that as the charge moves in the region of the magnetic field, the force acting on it acts as a centripetal force: therefore, the particle will start moving by unifom circular motion, with constant speed (because the magnetic force does no work on the particle, since it is perpendicular to the direction of motion).
So, the path of the particle will be a circle.