When two lineages split from a common ancestor, each accumulates different mutations over long periods of time. The number of mutations is proportional to the length of time that the two groups have been genetically separate. A scientist studies corresponding genes in two species. Which data would be most useful for determining the time when the split from the common ancestor occurred?
a. mutation rate and the number of mutations in each sequence
b. mutation rate and the number of nucleotides in each sequence
c. mutation rate and the number of nucleotides that differ between the two sequences
d. the number of repeated nucleotides and their specific locations in the two sequences