Which of the Following Processes Listed Below Represents the Experiment

Which of the following processes listed below represents the experiment for measuring an ionization energy ?
("E" represents a neutral E lement, "M" represents a M etal cation and "X" represents a nonmetal anion)

A) E (g) + e ^- → E ^- (g) + energy
B) E (g) + energy→ E⁺ (g) + e ^-
C) MX (g) + energy→ Mⁿ⁺ (g) + X^{n -} (g)
D) X - X (g) + energy→ 2 X · (g)
E) None of these