A hydrogen atom that has lost its electron is moving east in a region where the magnetic field is directed from south to north. It will be deflected:

Explanation

The hydrogen atom, which is effectively a proton in this context since it has lost its electron, is moving east in a magnetic field directed from south to north. To find the direction of the magnetic force acting on the proton, we can use the right-hand rule. For a positive charge like a proton, point your right thumb in the direction of the velocity (east), and your fingers in the direction of the magnetic field (north). The direction in which your palm pushes will indicate the direction of the magnetic force, which is upwards in this case. Therefore, the correct answer is up.Option B (down) is incorrect because the right-hand rule does not support this direction. Option C (north) is incorrect as the force does not act along the direction of the magnetic field but rather perpendicular to it. Option D (south) is also incorrect for the same reason; the magnetic force is not directed south based on the right-hand rule.