Protons move in a circle of radius $5\mathrm{.}80$ cmcm in a $0\mathrm{.}700$ TT magnetic field.

What value of electric field could make their paths straight?

In what direction must the electric field point?

The direction of the electric field must be in the direction of the velocity of the proton.The direction of the electric field must be perpendicular to both the velocity and the magnetic field, and must be in the opposite direction to the magnetic force on the protons.The direction of the electric field must be perpendicular to both the velocity and the magnetic field, and must be in the same direction as the magnetic force on the protons.The direction of the electric field must be in the direction of magnetic field.