A neutron collides head-on with a stationary hydrogen atom in ground state. Which of the following statement(s) is / are correct? (Assume that mass of the neutron and mass of the hydrogen atom are equal)

A. If the Kinetic energy of the neutron is less than 13.6 eV, collision must be elastic.
B. If the Kinetic energy of the neutron is less than 13.6 eV, collision must be inelastic.
C. Inelastic collision may take place on when the initial Kinetic energy of neutron is greater than 13.6 eV
D. If the kinetic energy of the neutron is more than 20.4 eV, collision must be inelastic.