Determine the number of scattering collisions a thermal neutron will experience on the average before being absorbed in H$$O$,$ D$$O$,238$U$,$ and cadmium, respectively.Determine the number of scattering collisions a thermal neutron will experience on the

average before being absorbed in $H_{2}O,D_{2}O,{?}^{238}U,$ and cadmium, respectively.