Of All the Possible Amino Acids, All Living Organisms Make

Of all the possible amino acids, all living organisms make use of only the same 20 amino acids. This supports the idea that

A) only a limited number of DNA mutations are possible.
B) bacteria, animals, and plants developed independently.
C) natural selection drives evolution.
D) all living things are derived from a single common ancestor.
E) only 20 amino acids exist on Earth.