The correct option is D Neoteny
Neoteny is the retention of juvenile characteristics in adult life. Neoteny has two forms depending upon the capability of individuals to breed pedomorphosis and paedogenesis. An example of neoteny is flightless birds, such as ostriches, emus, cassowaries and kiwis are believed to have evolved by retaining characters of chicks and losing an ability to fly. Physical proportions of these birds resemble those of the chicks of flighted birds. Hence, option C is correct.