What Is the Best Kind of Cells to Transplant into the Adult

What is the best kind of cells to transplant into the adult mammalian CNS?

A) Adult neurons of the same phenotype as those occupying the area into which the transplant will be made
B) Young neurons (1-2 days postnatal) of the same phenotype as those occupying the area into which the transplant will be made
C) Neurons from the autonomic nervous system
D) Neural stem cells
E) Late embryonic neurons