As you move down group one of the periodic table, what happens to the atomic radii? they increase, because of the higher number of occupied energy levels. they increase, because of the stronger attraction between electrons and the nucleus. they decrease, because of the weaker effective nuclear charge. they decrease, because of the lower number of protons.

The correct answer is the atomic radius increase because of the higher number of occupied energy levels.  

Atomic radius increases when going down a group. The valence electrons hold the higher levels because of the enhancing quantum number (n). As a consequence, the valence electrons get further away from the nucleus with the increase in n. The electron shielding inhibits these outer electrons from getting fascinated towards the nucleus. Therefore, they are held, and the resulting atomic radius is greater.