Final answer:
Molecular clocks are a method for D) estimating the time of divergence between species by assuming a constant rate of DNA evolution and comparing genetic differences.
Step-by-step explanation:
Molecular clocks are one of several ways to estimate divergence times between taxa, by comparing their gene sequences and assuming a constant rate of evolution over time. These clocks, also known as gene clocks or evolutionary clocks, are based on the premise that mutations in DNA accumulate at a steady average rate for a given region of DNA.
Therefore, by examining the amount of genetic differences between species, scientists infer how long it has been since those species diverged from a common ancestor. Importantly, the use of molecular clocks function as a complementary tool to other methods, such as the fossil record and geologic time scales, to understand the history of life on Earth.