Which of the Following Is NOT One the Standard Assumptions

Which of the following is NOT one the standard assumptions made when using molecular clocks to determine phylogeny?

A) The best alignment between homologous sequences always encompasses the least number of mutational changes.
B) Sequences that encode for essential catalytic portions of a protein change more slowly than portions without essential function.
C) Nucleotides in the position of third codon show more random mutation.
D) Artifactual mutations incorporated by PCR are high.
E) All of the above.