Sort the following phases in the order that they take place in neural development in vertebrates. Your answer would be a four-letter string composed of letters A to D only, e.g. DACB.
(A) Neurons are assigned specific characters according to the place and time of their birth.
(B) Neurons form synapses with other neurons or with muscle cells.
(C) Synaptic connections are refined and adjusted.
(D) Neurons extend axons and dendrites toward their target cells.