The genetic code (translating nucleotides into amino acids) is excellent evidence of what... (you may select more than one answer).
a. a single common origin of dna based life
b. the extremely strong selection against mutation in the code
c. convergence on a common code for translation
d. there is only one possible code that could have evolved so all organisms had to adapt to that code
e. a few organisms do have some variation which suggests it is not evidence for evolution.