The correct option is D move in a circular path with a uniform speed
If a positively charged particle moving in east direction enters a region of uniform magnetic field directed vertically upwards, it will move in a circular path with a uniform speed.
If a charged particle is moving in a direction perpendicular to a uniform magnetic field, then its trajectory will be a circle because the force F=qvB is always perpendicular to the velocity, and therefore centripetal.