In Which Direction Do Galaxies Evolve on the Hubble "Tuning

In which direction do galaxies evolve on the Hubble "tuning fork" classification scheme and what is the evolutionary significance of this diagram,shown in Figure 13-33 of Comins,Discovering the Essential Universe,6th ed.?

A) Present evidence suggests that galaxies do not evolve from one kind to another.
B) The "young" irregular and lenticular galaxies in the center of the "tuning fork" evolve to either elliptical galaxies if the material is metal-poor or spiral galaxies if the material is metal-rich.
C) Stars slowly die and the spiral arms slowly spin up and tighten to transform spiral galaxies into elliptical galaxies.
D) Elliptical galaxies slowly condense and spin up to form spiral galaxies, the increasing stellar collisions forming the interstellar material in the spiral arms.