The Best Explanation of What Defines a Multicellular Organism, as Opposed

Multiple Choice

The best explanation of what defines a multicellular organism, as opposed to a colonial one, is that:

A) a multicellular organism can exist and propagate as both a single-celled or a multicelled form.
B) a multicellular organism can only exist and propagate as a multicelled form.
C) a multicellular organism can only exist and propagate as a single-celled form.
D) a multicellular organism shows signs of cellular differentiation throughout its life cycle.