Donald Hebb's Major Contribution to Our Understanding of the Brain

Donald Hebb's major contribution to our understanding of the brain and its functions was his insight into

A) the different functions carried out by different regions of the brain.
B) the chemical processes within a single nerve cell.
C) the independent working of clusters of nerve cells.
D) the relation between individual nerve cells, larger networks and higher processes.
E) the physical location of memory, cognition and decision-making in the structures of the brain.