A proton moving with velocity v to the right (+x axis) enters a region of uniform magnetic field that points into the paper (-z axis). After the proton enters the field, it will be
undeviated.
deflected out of the plane opposite to the field (+z axis)
deflected downwards in the plane (-y axis).
deflected into the plane in the direction of the field (-z axis).
deflected upward in the plane (+y axis)