Why is it unwise to try to relate an organism's complexity with its size or number of cells?

A) A very large organism may be composed of very few cells or very few cell types.
B) A single-celled organism, such as a bacterium or a protist, still has to conduct all the complex life functions of a large multicellular organism.
C) A single-celled organism that is also eukaryotic, such as a yeast, still reproduces mitotically.
D) A simple organism can have a much larger genome.
E) A complex organism can have a very small and simple genome.