The Increase in Atomic Radius as One Progresses Within the Alkali

The increase in atomic radius as one progresses within the alkali metal family from element Z = 3 to Z = 87 in the periodic table can be attributed to

A) the increase in the principal quantum number of the outermost occupied orbital in the atom.
B) the decrease in the principal quantum number of the outermost occupied orbital in the atom.
C) the increase in the effective nuclear charge being experienced by the electron(s) in the outermost occupied orbital in the atom.
D) the decrease in the effective nuclear charge being experienced by the electron(s) in the outermost occupied orbital in the atom.
E) the increase in the secondary quantum number of the outermost occupied orbital in the atom.