For Which Process Is the Largest Amount of Energy Required $\rarr$

For which process is the largest amount of energy required?

A) Be⁺(g) $\rarr$ Be²⁺(g) + e^-
B) Be²⁺(g) $\rarr$ Be³⁺(g) + e^-
C) B²⁺(g) $\rarr$ B³⁺(g) + e^-
D) C(g) $\rarr$ C⁺(g) + e^-
E) C²⁺(g) $\rarr$ C³⁺(g) + e^-