What is needed to estimate species relatedness with a molecular clock?

Out of the following given choices;

A. DNA accumulates mutations at a regular rate

B. known mutation rate for a gene

C. the number of differences in DNA sequences for a gene in two species

D. the same gene identified in two species

E. All answers are corrects

The answer is E. The molecular clock used rates of mutation to determine the prehistoric time when two species that share a common ancestor diverged. The benchmarks for determining the mutation rate are often fossil or archaeological dates.