New Species Evolve from Older Ones

New species evolve from older ones. Why is it difficult to demonstrate this process?

A) In the grand scheme of things, there are not that many species, so this is a rare event.
B) There are none of the older species left.
C) The process typically takes a very, very long time, so it's difficult to see it reach completion, even in a lifetime.
D) New species don't evolve anymore, so we can't see it happen.
E) New species simply don't evolve from older ones, so it's impossible to demonstrate it in the real world.