Very important velocity selector question!!!?

Question

A velocity selector only lets through charged particles moving at a velocity v, where v = E/B (E is electric field and B is magnetic field). In order for the velocity selector to work properly:

a) The motion of the charged particle must be perpendicular to both the electric and magnetic fields.
b) Electric and magnetic field must be perpendicular to one another.
c) All of the above.
d) None of the above.

Answer 1

c) all of the above.

The motion of the charged particle must be perpendicular to both the electric and magnetic field and both fields must be perpendicular to each other.