Why is it that all neurons in a healthy adult brain have made appropriate connections?

    a.    We are born with all connections formed.
    b.    Chemical messages from our muscles tell our brain how many neurons to form, and that number perfectly matches the connections required.
    *c.    If an axon does not make the appropriate connections by a certain age, it dies.
    d.    Connections form rapidly, but we learn to use whatever connections have formed.