An Ionized Atom Having Z Protons Has Had All but One

Multiple Choice

An ionized atom having Z protons has had all but one of its electrons removed. If R is the radius of the ground state electron orbit in atomic hydrogen, then what is the radius of the shell of the
Remaining electron in the ionized atom?

A) $R$
B) $Z ^ { 2 } R$
C) $R / Z$
D) $Z R$
E) $R / Z ^ { 2 }$