When a Substance Changes Phase, from Solid to Liquid or Liquid

When a substance changes phase, from solid to liquid or liquid to vapor and vice versa, there is no change in temperature, even though heat is being added or removed. Why is there no change in temperature?

A) During a phase change, energy is used to break/establish the intermolecular bonds rather than stored as kinetic energy of the molecules.
B) During a phase change, temperature is not well defined since there are two phases involved.
C) During a phase change, energy is needed to overcome the gravitational pull.
D) During a phase change, the temperature measured is the last temperature of the measuring device.
E) None of the above.