The Following Questions Refer to the Information Below -Which Kind of DNA Should Provide the Best Molecular Clock

The following questions refer to the information below.
A researcher compared the nucleotide sequences of a homologous gene from five different species of mammals with the homologous human gene. The sequence homology between each species' version of the gene and the human gene is presented as a percentage of similarity.
$$\begin{array} { l c } \text { Species } & \text { Percentage } \\\hline \text { Chimpanzee } & 99.7 \\\text { Orangutan } & 98.6 \\\text { Baboon } & 97.2 \\\text { Rhesus Monkey } & 96.9 \\\text { Rabbit } & 93.7\end{array}$$

-Which kind of DNA should provide the best molecular clock for gauging the evolutionary relatedness of several species whose common ancestor became extinct billions of years ago?

A) that coding for ribosomal RNA
B) intronic DNA belonging to a gene whose product performs a crucial function
C) paralogous DNA that has lost its function (i.e., no longer codes for functional gene product)
D) mitochondrial DNA
E) exonic DNA that codes for a non-crucial part of a polypeptide