An Ionized Atom Having $Z$ Protons Has Had All but One of Its Electrons Removed

Multiple Choice

An ionized atom having $Z$ protons has had all but one of its electrons removed. If $E$ is the total energy of the ground state electron in atomic hydrogen, then what is the total energy of the remaining electron in the ionized atom?

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