²³⁵U Is Readily Made Fissionable by a Thermal Neutron but ²³⁸U

Multiple Choice

²³⁵U is readily made fissionable by a thermal neutron but ²³⁸U is not because:

A) the neutron has a smaller binding energy in ²³⁶U
B) the neutron has a smaller excitation energy in ²³⁶U
C) the potential barrier for the fragments is less in ²³⁹U
D) the neutron binding energy is greater than the barrier height for ²³⁶U and less than the barrier height for ²³⁹U
E) the neutron binding energy is less than the barrier height for ²³⁶U and greater than the barrier height for ²³⁹U