The energy required to remove the electron from the first excited state ($n=2$) of $He^+$ is

For a hydrogen-like ion, $E_n = -13.6 \cdot Z^2/n^2\,eV$. For $He^+$ ($Z=2, n=2$): $E_2 = -13.6 \cdot 4/4 = -13.6\,eV$. Energy to take the electron from $n=2$ to $n=\infty$ (where $E=0$) is $|E_2| = 13.6\,eV$. **Option B ($3.4\,eV$) is the corresponding value for *hydrogen*'s $n=2$ — a classic trap.**